Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Pontus Pihlgren]

On Tue, Jun 16, 2015 at 04:28:16AM +, tony duell wrote:
> 
> I am of course counting all the transistors inside that chip.

Well, that was obvious. But it raises an interesting point, today you 
can cram a whole computer in the footprint of the simplest DIP carrier. 
For the same price point and same reliablity. Is it then overkill if you 
choose to use thousands of those transistor over using just 10 ?

Similar to Mark's example of using just the first bytes of an SD card 
with gigabytes of storage.

> This is one of my main dislikes with USB. It is so complicated that you 
> have to use a microcontroller. Unlike any of the more sane interfaces that
> you can implement with simple logic if you want to.

I completely agree, I detest USB for various reasons. However consider 
this:

As I said, I have used the Teensy to interface an old 11/70 front panel 
with simh. One possibility I've considered is to let the Teensy present 
itself as USB mass storage when first attached to a PC. On this mass 
storage I would put a special version of simh and 11/70 system images. 
When this version of simh is run, it will instruct the Teensy to present 
itself as the front panel interface instead.

So, I can bring my 11/70 front panel to any friend with a suitable 
computer and show him/her the ropes :)

Admittedly, the Teensy doesn't have enough storage for this, but it 
shows the flexibilty of USB coupled with a microcontroller.

/P

Re: Reviving a VAX-11/750

[Mattis Lind]

In my efforts to understand the problem with the Cache/TB Diagnostics I
tried to run it under 11/750 simulator in SimH. It fails too!

ECKAL -- VAX 11/750 Cache/TB Diagnostic
HALT instruction, PC: 2608 (MTPR #F,#26)

Although not the same location.

On the real machine:

@?ECKAL -- VAX 11/750 Cache/TB Diagnostic

3488  06


Trying to disassemble at 3488 in SimH gives me:

EXTZV @-1D(R7),#0,#0,(R8)+


The EXTZV is supposed be "Extract Zero-Extended Field"


I have never done any VAX-11 assembly coding so this is very new ground for
me... As far as I understand the diagnostic starts at address 200. But then
understanding what it does without the listing... Well. A long journey for
me.


/Mattis

2015-06-15 22:07 GMT+02:00 Mark J. Blair :

>
> > On Jun 15, 2015, at 11:59 , tony duell  wrote:
> >
> >
> >> I also may dump the console firmware PROMs at some point. I've already
> done some preliminary
> >> disassembly of the TU58 firmware.
> >
> > I am pretty sure I dumped all the PROMs and PALs in the CPU of my 11/730
> (but not the ones in the
> > R80) long before there was a bitsavers. I can see if I can find the
> dumps. What I don't have is the
> > Remote Diagnostic ROMs (this was another pair of 2K*4 ROMs that plug
> into sockets on the WCS
> > board and which run on the 8085). So no dumps of that.
>
> I have three WCS cards, including the one in my machine, but none of them
> have the remote diagnostic option.
>
> --
> Mark J. Blair, NF6X 
> http://www.nf6x.net/
>
>

Re: Fairchild

[wulfman]

Maybe Univac?



On 6/15/2015 9:58 PM, Zane Healy wrote:
> Does anyone happen to know what sort of computers Fairchild would have been 
> using in the late 60's for design work?
>
> Zane
>
>
>
>


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RE: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[tony duell]

> >
> > I am of course counting all the transistors inside that chip.
> 
> Well, that was obvious. But it raises an interesting point, today you
> can cram a whole computer in the footprint of the simplest DIP carrier.
> For the same price point and same reliablity. Is it then overkill if you
> choose to use thousands of those transistor over using just 10 ?

Is it as reliable, though? You will get no argument from me that the _same 
design_
is more reliable the more 'LSI' it is -- that is a processor as a single chip 
is more
reliable than the same design in TTL which in turn is more reliable than the 
same design
in discrete transistors. But when you compare different designs, I am not 
conviced. My 
experience is that I have had to replace many more LSI ICs than TTL and many 
more TTL chips
than transistors (power transistors, choppers, line output transistors 
excpeted!). I am not at all 
convinced that a microcontroller is as reliable as a 555 timer. After all, 
microcontrollers presumably
store their firmware in some kind of flash memory which is going to suffer from 
bit-rot. A 555
doesn't.

> Similar to Mark's example of using just the first bytes of an SD card
> with gigabytes of storage.

Again, I wonder if the data retention time decreases as the number of bits
per device increases. Intuitively it should. Mind you, any SD card is probably
going to be more reliable than a real TU58 tape now :-)

-tony

Re: Fairchild

[Chuck Guzis]

On 06/15/2015 09:58 PM, Zane Healy wrote:

Does anyone happen to know what sort of computers Fairchild would have been 
using in the late 60's for design work?


Fairchild, even in the 60s had many divisions.  Which one are you 
thinking of? (Not that I can provide an answer...)


--Chuck

Re: Serial UNIBUS Repeater?

[Ethan Dicks]

On Tue, Jun 16, 2015 at 12:20 AM, tony duell  wrote:
> [My 11/730]
>
>> Sorry to hear that it's been decabled. Take your time to route those cables 
>> through the bottom pan properly,
>
> Yes, it's going to be a lot of work to get it back together.
>
> I think I am going to start (when I have got the machine room straightened 
> out, etc) with the 2 parts
> of the cable tray on the bench. Route all the cables. Fit the tray to the 
> rack, then the CPU box slides, then
> the CPU box, and connect everything up. And get it right first time, I do not 
> want to be changing things here.

The VAX-11/730 System Installation Guide (EK-SI730-IN-003) has
information about how to load the catch pan.  Given all the 90 degree
and 45 degree folds, it's the sort of thing you only want to do to a
fresh cable once.  There might also be a specific 11/730-Z detailed
installation manual.  I have a memory of one but don't know the part
number.

My memories of those days (we had two 11/730s) is that if you don't do
it the way they did, either things won't reach (or be on the wrong
side to fit into bulkhead connectors) or you'll have to redo it.

https://archive.org/details/bitsavers_decvax730E83_4699164

> Exactly. Which is one reason I am considering a Unibus expansion box. Keep 
> the CPU with a standard
> fixed configuration and have the expansion box with simpler cable routing for 
> things I want to change.

We did have that.  It was nearly essential.  We had the CPU, memory,
and the default (as shipped) peripherals.  Everything else went into
our BA-11K

FWIW, we only had the RB80/RL02 version.  Tape was a TU80 with the
controller in the BA-11K.  Our COMBOARDs also went in the BA-11K, but
that was also for our convenience of swapping out our own product for
testing and firmware swaps, etc.

-ethan

RE: using new technology on old machines

[tony duell]

> Sure, the pre-manufactured boards can allow you to prototype quickly... but
> I think Tony is kind of bemoaning the loss of the "old way" and I respect
> that ... I kind of miss it myself, even though I wasn't there to experience
> it first-hand ...

It's also that this is the 'classic computers' list. To me, classic computing 
means rather
more than just the hardware. It also covers the design and construction 
methods, technology
and so on. And there seems to be precious little of that in a modern 
microcontroller acting
as a clock oscillator.

I find it odd that people want to have a lights-and-switches panel, but are 
prepared to totally
adulterate the hardware of the machine that drives it.

As an aside, when I restore m 11/730 I am in 2 minds as to what to do about the 
microcode load
device. a TU58 emulator is certainly convenient, but I actually would rather 
get the real tape drives
working if at all possible. After all that is what the machine was designed to 
use.



> How are everyone's parts bins so empty? My dad is a practicing EE of over

Mine isn't, but then you knew that, right :-). When I moved house recently I 
think I had
over 30 packing boxes of modern-ish components and more of valves and CRTs. Not
counting the dozen or so boxes of PCBs (some to use, some to raid for parts). 

-tony

Re: using new technology on old machines

[Mark J. Blair]

> On Jun 16, 2015, at 06:54, tony duell  wrote:
> As an aside, when I restore m 11/730 I am in 2 minds as to what to do about 
> the microcode load
> device. a TU58 emulator is certainly convenient, but I actually would rather 
> get the real tape drives
> working if at all possible. After all that is what the machine was designed 
> to use.


I'll consider using my real TU58 drive instead of an emulator when I find a 
working TU58 cartridge. So far, that is foreign to my experience. :(

I've cleaned up my drive and replaced the capstan rubber, and I think my drive 
is probably just fine. The problem is the media, which in my opinion was a poor 
mechanical design when new. I also thoroughly distrust the similar mechanism of 
the larger QIC tapes.

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Mark J. Blair]

> On Jun 16, 2015, at 06:46, tony duell  wrote:
> 
> Again, I wonder if the data retention time decreases as the number of bits
> per device increases. Intuitively it should. Mind you, any SD card is probably
> going to be more reliable than a real TU58 tape now :-)

I think that paper tape, used outdoors on a rainy day, is likely to be more 
reliable than a real TU58 tape. :)

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Chris Elmquist]

Choosing the larger card is, IMO, the right answer because you don't
actually waste the space, you extend the life significantly because the
wear leveling will spread your 256K across the entire flash region.
The larger that region, the less often you re-write the same cells,
thereby extending the life of all the cells.

Chris

On Monday (06/15/2015 at 03:06PM -0700), Mark J. Blair wrote:
> 
> > On Jun 15, 2015, at 14:56 , Dave G4UGM  wrote:
> > 
> > A friend of mine refused to buy modern SD Cards because there was no way he
> > was going to fill them. Trouble is that although smaller SD cards were
> > available they were way more expensive (being discontinued and therefore
> > rare and valuable).. He struggled with buying a larger card only to waste
> > most of it, or buy a smaller one and waste his money
> 
> 
> I had that same mental hangup when thinking about how I might design an SD 
> card based TU58 emulator in the same form factor as a TU58 cartridge (still 
> on my to-do list, by the way). How was I going to implement the user 
> interface? It's not like there's much room for an LCD or buttons on the edge 
> of a TU58 cartridge. Then it finally hit me: SD cards are cheaper than TU58 
> cartridges ever were. So why not just use the first 256k, ignore the rest of 
> the card, and swap cards exactly the way one would swap TU58 cartridges, with 
> one image on each card? Yeah, 99% of the card is "wasted", but they're 
> presently cheap and plentiful enough to ignore that.
> 
> Ok, I might actually have the emulator read a file from a DOS filesystem 
> rather than using the first 256k of raw blocks. But it'll probably just be a 
> fixed filename with no controls to select a different one, and the 
> expectation that an entire (cheap, plentiful) SD card will be devoted to each 
> tape image. At least this way, other things can also be on the card, so it 
> doesn't need to be wasted if not needed.
> 
> Your friend should understand that the larger card that he would be "wasting" 
> probably has less silicon in it than the older one with less capacity. The 
> cheapest card that is reliable, fast enough and large enough for his task is 
> the best one to get, even if it's much larger than he needs. Just one of the 
> weird parts of the Moore's Law curve!
> 
> Hmm, this reminds me that back in the day, floppy disks were expensive. We 
> have it easy with cheap and plentiful SD cards nowadays. But maybe my 
> perspective is different as an employed adult rather than a teenager with 
> limited funds? Anyway, SD cards seem to be cheap enough to be nearly 
> disposable nowadays.
> 
> -- 
> Mark J. Blair, NF6X 
> http://www.nf6x.net/

-- 
Chris Elmquist

Re: using new technology on old machines

[Noel Chiappa]

> From: tony duell

> One method that works for me is that if you are buying a fairly cheap
> part, buy 10 of them and put the rest in stock. Or more than 10 if it
> is something really common.

I suspect a lot of us do that - that's why I have tubes of 4164's, etc, for
instance. It makes a lot of sense, because it's trivial to implement - it's
just as much work to order 10 of something, as 1.

But that model isn't really the best, because a lot of the time one winds up
needing something one doesn't already have. Which is why it's better to lay
in a diversified stock up front. E.g. in wood screws (I do a lot of work in
wood, mostly furniture), I have a fairly comprehensive collection; from #6
through #12, all the available lengths (not the very longest ones, though),
counter-sunk and round-headed, with both slot and Phillips drive.

But doing so in IC's - oi vey! Just in TTL alone, there are dozens of common
parts (hundreds, if you count the more obscure ones), and then you get into
the whole 74, 74S, 74LS, 74ALS, 74L, 74H, 74F, yadda-yadda. Of course, most
of the variants one would never need, but one can't get by with just, e.g.
LS; e.g. if I ever get my wish and wind up with a PDP-11/45, that's mostly S,
IIRC.

I wish there was some _easy_ way to lay in a stock of the most common TTL
IC's - e.g. some kind of kit one could buy - but alas, I don't know of any.
(Hence my dream of finding and acquiring someone else's collection! :-)
Suggestions for the source of such a good diversified 'starter kit' welcome...

Noel

Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Chris Elmquist]

On Monday (06/15/2015 at 10:14PM -0700), Mark J. Blair wrote:
> 
> > On Jun 15, 2015, at 21:59, tony duell  wrote:
> > Even though there are at least 4 different USB connectors
> 
> Ok, you got me there! When I was working for a GPS startup, I used mini-B on 
> everything I designed with USB (always devices, never hosts, and no need for 
> USB OTG). Then we got bought by a cell phone company and now everything's a 
> godawful mix of mini-B and micro-B, with OTG thrown in there, too. Grrr!

I'm going straight to hell because I recently participated in a customer
design where they wanted to change the USB function on a device we
designed for them from host mode to device mode but they didn't want to
change the connector on the box.

So, now you have to use a Type A to Type A cable to connect this box to
your computer.

That is just really, really messed up and I honestly tried to make it
right but it was like pushing a rope.

I hope my friends will visit me in prison.

Chris
-- 
Chris Elmquist

Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Chris Elmquist]

On Tuesday (06/16/2015 at 07:24AM -0700), Mark J. Blair wrote:
> 
> > On Jun 16, 2015, at 06:46, tony duell  wrote:
> > 
> > Again, I wonder if the data retention time decreases as the number of bits
> > per device increases. Intuitively it should. Mind you, any SD card is 
> > probably
> > going to be more reliable than a real TU58 tape now :-)
> 
> I think that paper tape, used outdoors on a rainy day, is likely to be more 
> reliable than a real TU58 tape. :)

I can vouch for that.

-- 
Chris Elmquist

Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Mark J. Blair]

> On Jun 16, 2015, at 07:36, Chris Elmquist  wrote:
> So, now you have to use a Type A to Type A cable to connect this box to
> your computer.
> 
> That is just really, really messed up and I honestly tried to make it
> right but it was like pushing a rope.
> 
> I hope my friends will visit me in prison.

Sounds to me like you are more of a victim than a perpetrator here. Isn't there 
some OSHA regulation against USB A to A cables? :)


-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: O/S design & implementation - was Re: FPGA tricks - Re: using new technology on old machines

[Paul Koning]

> On Jun 15, 2015, at 9:21 PM, ben  wrote:
> 
> On 6/15/2015 7:11 PM, Paul Koning wrote:
>> 
>>> On Jun 15, 2015, at 8:09 PM, ben  wrote:
>>> 
>>> On 6/15/2015 4:42 PM, Toby Thain wrote:
>>> 
 I think Tanenbaum should be fine? A lot of it is fairly
 timeless.
>>> 
>>> The latest version is *useless*. The racoons on the cover tells
>>> alot.
>> 
>> Or you could just read “The structure of the THE operating system” by
>> E.W.Dijkstra, and follow its principles.
> 
> a)  Not online to my knowledge

http://www.cs.utexas.edu/users/EWD/ewd01xx/EWD196.PDF — the same site that has 
the full archive of all EWD papers (except for some very early ones that have 
been lost) — a total of 1300 or so.  

> b)  Most likely in German

None are in German, naturally, since Dijkstra was Dutch.  Some early ones are 
in Dutch, but this one is in English.

> c)  and the most important thing ... I do not have any Mag Tape

Not relevant; the THE OS does not rely on magtapes.  It uses drum for paging 
and spooling, but the design is nicely layered so the system also works without 
drum (this is explicitly mentioned in one of the reports on its development).  

In any case, I did not point to this paper as a specific OS to implement, but 
rather as a demonstration of how to design a modest size but quite useful OS, 
with very modest effort and extremely high reliability.

EWD1303 (http://www.cs.utexas.edu/users/EWD/ewd13xx/EWD1303.PDF) is another 
note about that effort, looking back from 2000.

paul

Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Chris Elmquist]

On Tuesday (06/16/2015 at 07:43AM -0700), Mark J. Blair wrote:
> 
> > On Jun 16, 2015, at 07:36, Chris Elmquist  wrote:
> > So, now you have to use a Type A to Type A cable to connect this box to
> > your computer.
> > 
> > That is just really, really messed up and I honestly tried to make it
> > right but it was like pushing a rope.
> > 
> > I hope my friends will visit me in prison.
> 
> Sounds to me like you are more of a victim than a perpetrator here. Isn't 
> there some OSHA regulation against USB A to A cables? :)

well, you know, it's a different world these days.  You go to these places
down dark alleys, surrounded by shady characters and you can buy them.

-- 
Chris Elmquist

Re: O/S design & implementation - was Re: FPGA tricks - Re: using new technology on old machines

[Paul Koning]

> On Jun 15, 2015, at 7:10 PM, Sean Caron  wrote:
> 
> ...
> 4. Madnick/Donovan Operating Systems or Donovan's Systems Programming ...
> were, I imagine, the canon of the 70s and early 80s ... these are written
> mostly with the S/360 in mind …

If it’s written with 360 operating systems in mind, I’d steer clear.  I don’t 
know of much in the way of valuable OS design principles to be found there 
(except perhaps the lessons reported in “the mythical man month” or in Tom 
Watson’s famous anecdote about the size of the CDC 6600 development effort).

paul

Re: O/S design & implementation - was Re: FPGA tricks - Re: using new technology on old machines

[Paul Koning]

> On Jun 16, 2015, at 2:49 AM, ben  wrote:
> 
>> ...
>> 
> Since the computer I designed is a *small* computer, 8 & 16 bit operating 
> systems is what I am looking at for ideas. This is a 18 bit cpu with the 
> concept, byte access of memory needs true 18 bit addressing
> and 16 bits is bit small for general 1970's data. Think of it as a something 
> like a 9 bit 6800 cpu.

If you’re looking at 1960s designs, you should be fine even if the machine had 
wider words.  By the standards of that era, any modern computer (probably 
including the one in your microwave oven) is *large*.  For example, the THE OS 
memory footprint is about 16k words (48k bytes), and that includes not just 
what we think of as a kernel but also all the device drivers and a bunch of 
language support library code.  Other designs from that era are smaller still.

paul

RE: using new technology on old machines

[Dave G4UGM]

> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of tony
duell
> Sent: 16 June 2015 14:55
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: RE: using new technology on old machines
> 
> 
> 
> > Sure, the pre-manufactured boards can allow you to prototype
> > quickly... but I think Tony is kind of bemoaning the loss of the "old
> > way" and I respect that ... I kind of miss it myself, even though I
> > wasn't there to experience it first-hand ...
> 
> It's also that this is the 'classic computers' list. To me, classic
computing means
> rather more than just the hardware. It also covers the design and
> construction methods, technology and so on. And there seems to be
> precious little of that in a modern microcontroller acting as a clock
oscillator.
> 

There isn't., but some-times we have to compromise, and sometimes we choose
to compromise. I looked at the circuit of the M484 and I might not have the
parts in the parts box...
.. its also a nasty hybrid design with DC biased NPN and PNP transistors. I
find it ugly and can see it being a pig to debug, though it simulates fine
in LTspice...

> I find it odd that people want to have a lights-and-switches panel, but
are
> prepared to totally adulterate the hardware of the machine that drives it.

There sometimes isn't enough hardware to go round. I would like a front
panel for my SBC6120 but I don't think DEC built a machine with a 61xx chip
and a front panel...

> 
> As an aside, when I restore m 11/730 I am in 2 minds as to what to do
about
> the microcode load device. a TU58 emulator is certainly convenient, but I
> actually would rather get the real tape drives working if at all possible.
After
> all that is what the machine was designed to use.
> 

Nice if you can get it to work.

> 
> 
> > How are everyone's parts bins so empty? My dad is a practicing EE of
> > over
> 
> Mine isn't, but then you knew that, right :-). When I moved house recently
I
> think I had over 30 packing boxes of modern-ish components and more of
> valves and CRTs. Not counting the dozen or so boxes of PCBs (some to use,
> some to raid for parts).

I have a good selection of TTL but I am not longer sure if it works. I think
a lot of NOS TTL has rotted internal connecting wire. 

> 
> -tony

Dave
G4UGM

Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Alexandre Souza]

Again, I wonder if the data retention time decreases as the number of bits
per device increases. Intuitively it should. Mind you, any SD card is 
probably

going to be more reliable than a real TU58 tape now :-)
I think that paper tape, used outdoors on a rainy day, is likely to be more 
reliable than a real TU58 tape. :)


   You got a thumbs-up! (In Brazil we call it "Joinha") :)

Re: using new technology on old machines

[geneb]

On Tue, 16 Jun 2015, Noel Chiappa wrote:


I wish there was some _easy_ way to lay in a stock of the most common TTL
IC's - e.g. some kind of kit one could buy - but alas, I don't know of any.
(Hence my dream of finding and acquiring someone else's collection! :-)
Suggestions for the source of such a good diversified 'starter kit' welcome...


How about this:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_84961_-1


g.

--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
http://www.diy-cockpits.org/coll - Go Collimated or Go Home.
Some people collect things for a hobby.  Geeks collect hobbies.

ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
http://scarlet.deltasoft.com - Get it _today_!

On the Emulation of TU58s

[Mark J. Blair]

As long as we're talking philosophy, what do y'all think about emulating the 
TU58 drive, vs. emulating the TU58 *tape*?

I cannot properly express my opinion of that tape cartridge design even if I 
violate list rules about use of profanity. But the drive itself isn't all that 
bad, aside from not having enough motors to manipulate a well-designed tape 
cartridge mechanism.

Emulating the whole tape drive is pretty easy since it helpfully interfaces 
over a plain old asynchronous serial port. But replacing the whole drive with 
an emulator, or worse yet tethering its computer to a modern computer, leaves a 
bit of an empty feeling if one likes their vintage machines to be original. 
There's something missing when you don't hear the drive whirring, and the 
system boot completes within a modern attention span.

But what about emulating the tape cartridge, instead? Imagine a gizmo in the 
form factor of a TU58 cartridge, containing a wheel for the capstan roller to 
engage, but connected to an encoder instead of the ***  * 
**  belt drive of an original cartridge? Where the tape would normally be 
exposed, there is instead a magnetic head which rests against the tape drive 
head like in one of those gizmos for injecting line level audio into an audio 
cassette drive. It might need an external power source, but for the sake of 
argument, let's pretend that a suitable rechargeable battery can be embedded. 
Maybe it has an SD card slot on the rear, or maybe it looks just like a real 
TU58 cartridge when inserted, and you swap the whole thing to change tapes 
(this is open for discussion).

Would this be more or less acceptable in terms of keeping the system as close 
to original as possible, vs. unplugging the original drive and plugging in a 
drive emulator?

No, I'm not going to build the thing. I'll just build my TU58 drive emulator to 
fit in the cartridge slot but plug into the computer in place of the original 
drive, with the cables snaked through the original drive mechanism. And I'll 
feel a little bit dirty, but the thing will work reliably and will be easy to 
implement. I'm just curious about the philosophical implications of my silly 
cartridge emulator idea.

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: using new technology on old machines

[Mark J. Blair]

> On Jun 16, 2015, at 08:19, geneb  wrote:
> 
> On Tue, 16 Jun 2015, Noel Chiappa wrote:
> 
>> I wish there was some _easy_ way to lay in a stock of the most common TTL
>> IC's - e.g. some kind of kit one could buy - but alas, I don't know of any.
>> (Hence my dream of finding and acquiring someone else's collection! :-)
>> Suggestions for the source of such a good diversified 'starter kit' 
>> welcome...
>> 
> How about this:
> http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_84961_-1

Very nice! I might just order one of those.

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: using new technology on old machines

[wulfman]

2.47 per each ic is kinda expensive

but then again i have 10s of thousands of each 74 series part there was
ever made
been collecting on ebay for 15 years and can repair most any old
computer there is
my hobby is old arcade boards and have the largest collection in arizona

some of the tough parts are the bipolar roms used on boards
they get hot run hot and fail


On 6/16/2015 8:19 AM, geneb wrote:
> On Tue, 16 Jun 2015, Noel Chiappa wrote:
>
>> I wish there was some _easy_ way to lay in a stock of the most common
>> TTL
>> IC's - e.g. some kind of kit one could buy - but alas, I don't know
>> of any.
>> (Hence my dream of finding and acquiring someone else's collection! :-)
>> Suggestions for the source of such a good diversified 'starter kit'
>> welcome...
>>
> How about this:
> http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_84961_-1
>
>
>
> g.
>


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Re: using new technology on old machines

[geneb]

On Tue, 16 Jun 2015, Mark J. Blair wrote:




On Jun 16, 2015, at 08:19, geneb  wrote:

On Tue, 16 Jun 2015, Noel Chiappa wrote:


I wish there was some _easy_ way to lay in a stock of the most common TTL
IC's - e.g. some kind of kit one could buy - but alas, I don't know of any.
(Hence my dream of finding and acquiring someone else's collection! :-)
Suggestions for the source of such a good diversified 'starter kit' welcome...


How about this:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_84961_-1


Very nice! I might just order one of those.


They also offer 4000 series, transistor, resistor, and capacitor 
collections.


g.

--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
http://www.diy-cockpits.org/coll - Go Collimated or Go Home.
Some people collect things for a hobby.  Geeks collect hobbies.

ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
http://scarlet.deltasoft.com - Get it _today_!

Re: using new technology on old machines

[Pontus Pihlgren]

On Tue, Jun 16, 2015 at 01:54:56PM +, tony duell wrote:
> 
> I find it odd that people want to have a lights-and-switches panel, but are 
> prepared to totally
> adulterate the hardware of the machine that drives it.
> 

Are you honestly suggesting that I should rebuild a PDP-11/70 
from things I have in my partsbin?

'cause that is what it sounds like.

/P

RE: using new technology on old machines

[tony duell]

> >
> > I find it odd that people want to have a lights-and-switches panel, but are 
> > prepared to totally
> > adulterate the hardware of the machine that drives it.
>
> 
> Are you honestly suggesting that I should rebuild a PDP-11/70
> from things I have in my partsbin?

You have to admit it would be an interesting and educational project :-)

> 'cause that is what it sounds like.

No, not really. If you have a front panel from an otherwise non-existant 
machine then
it makes sense to drive it any way you can. I was thinking more of the PDP12 
that started
this. 

-tony

Re: using new technology on old machines

[Pontus Pihlgren]

On Tue, Jun 16, 2015 at 03:58:51PM +, tony duell wrote:
> > Are you honestly suggesting that I should rebuild a PDP-11/70
> > from things I have in my partsbin?
> 
> You have to admit it would be an interesting and educational 
> project :-)

Oh, very much! Then we could have a discussion about using 
modern switching power supplies ot not ;-)

/P

RE: On the Emulation of TU58s

[tony duell]

> 
> As long as we're talking philosophy, what do y'all think about emulating the 
> TU58 drive, vs. emulating the TU58 > *tape*?
> 
> I cannot properly express my opinion of that tape cartridge design even if I 
> violate list rules about use of 
> profanity. But the drive itself isn't all that bad, aside from not having 
> enough motors to manipulate a 
> well-designed tape cartridge mechanism.

The tape cartridge (along with QIC cartridges, etc) is an interesting design. 
Of course the general problem is 
to run the tape at constant linear speed past the head while winding it off one 
reel onto the other. In general
there have been 3 solutions to this.

One is to drive the tape itself using a capstan and maybe a pinch roller. Then 
have the takeup spool
driven too fast with a slipping clutch in-line. And a weak brake on the supply 
spool. This of course is what
was done in audio recorders (reel to reel and cassette), Video recorders 
(ditto), etc.

Another is to simply drive the takeup spool but to measure the speed of the 
outside of the tape wound on
it. thus keeping a constant tape speed. I had forgotten this one until I 
realised that's how the Cipher F880 
works. Or maybe to run the tape round a rotating guide that has a tacho disk on 
it. I've not seen that used,
but I bet it was somewhere.

The last is to drive the outside of the tape wound on the spools. Of course 
this keeps constant tape speed.
Mechanically it is by far the simplest. All you need is one motor driving a 
belt that is tensioned against the 
outside of the tape spools. This is how the TU58, etc, work. The problem is due 
to the physical properties
of the tape and belt, which leads to tape wear and damage and a short life.
 
There are at least 2 types of TU58 cartridge (DEC called them 'metal base' and 
'plastic base' I think. Is
one any better than the other?

Incidentally, given the fact that a constant motor speed -> constant tape 
speed, it should be possible to
make a device to put the timing track on a blank tape for the TU58. Has anyone 
done that?

> But what about emulating the tape cartridge, instead? Imagine a gizmo in the 
> form factor of a TU58 cartridge, 
> containing a wheel for the capstan roller to engage, but connected to an 
> encoder instead of the *** 
>  * **  belt drive of an original cartridge? Where the 
> tape would normally be exposed, there is 

Now that I want to see!

Even a module containing coupling head and encoder disk that slots into a TU58 
drive and which links
to an external box of electronics containing the SD card, etc, would be 
interesting.

You would, of course, not know which track it was reading, so you would have to 
output 2 blocks, one on
each track, at once. And how would you detect it was writing? Look for an extra 
signal at the coupling head
or something?

-tony

Re: O/S design & implementation - was Re: FPGA tricks - Re: using new technology on old machines

[ben]

On 6/16/2015 8:56 AM, Paul Koning wrote:



On Jun 16, 2015, at 2:49 AM, ben  wrote:


...


Since the computer I designed is a *small* computer, 8 & 16 bit
operating systems is what I am looking at for ideas. This is a 18
bit cpu with the concept, byte access of memory needs true 18 bit
addressing and 16 bits is bit small for general 1970's data. Think
of it as a something like a 9 bit 6800 cpu.


If you’re looking at 1960s designs, you should be fine even if the
machine had wider words.  By the standards of that era, any modern
computer (probably including the one in your microwave oven) is
*large*.  For example, the THE OS memory footprint is about 16k words
(48k bytes), and that includes not just what we think of as a kernel
but also all the device drivers and a bunch of language support
library code.  Other designs from that era are smaller still.


There is *NO* computer in my MICROWAVE!
I have the good kind! ( I need to fix the the defrost and half power
settings someday).  Timer dings when food is cooked.


paul

16K words seems right, for that era as core was swapped in and
out to run system and program threads. Since TIME SHARING was the
big development feature of that era, I am ignoring most main frame
operating systems. Single user with small memory and disk I/O as
similar to the mid 1970's is my goal.
But this is all I have to say, as I want stick to real hardware on this
list.
Ben.

RE: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[tony duell]

> > Sounds to me like you are more of a victim than a perpetrator here. Isn't 
> > there some OSHA regulation against 
> > USB A to A cables? :)

> well, you know, it's a different world these days.  You go to these places
> down dark alleys, surrounded by shady characters and you can buy them.

One of the local pound shops (~= dollar stores) sells a cable with a USB A plug 
on 
one end and a pair of RCA phono plugs on the other. I am told this makes sense 
for
some device-or-other...

Actually, IIRC a USB A male->female cable violates the spec...

-tony

RE: using new technology on old machines

[tony duell]

[Build your own 11/70]

> Oh, very much! Then we could have a discussion about using
> modern switching power supplies ot not ;-)

As opposed to the original 11/70 switching supply?

-tony

Re: using new technology on old machines

[Pontus Pihlgren]

On Tue, Jun 16, 2015 at 04:18:03PM +, tony duell wrote:
> [Build your own 11/70]
> 
> > Oh, very much! Then we could have a discussion about using
> > modern switching power supplies ot not ;-)
> 
> As opposed to the original 11/70 switching supply?

I would suspect that modern switchers are more efficient. If I 
wanted to have one running for any longer extent I would 
consider an "upgrade". Only reversible changes of course.

/P

RE: using new technology on old machines

[tony duell]

> 
> > > Oh, very much! Then we could have a discussion about using
> > > modern switching power supplies ot not ;-)
> >
> >  As opposed to the original 11/70 switching supply?
> 
> I would suspect that modern switchers are more efficient. If I
> wanted to have one running for any longer extent I would
> consider an "upgrade". Only reversible changes of course.

Quite probably, but the modern mains-side switcher is more 
troublesome and a lot less pleasant to repair. I think I'll stick
with the room-heater in my 11's :-)

-tony

RE: using new technology on old machines

[tony duell]

> > It's also that this is the 'classic computers' list. To me, classic
> > computing means
> > rather more than just the hardware. It also covers the design and
> > construction methods, technology and so on. And there seems to be
> > precious little of that in a modern microcontroller acting as a clock
> > oscillator.
>
> 
> There isn't., but some-times we have to compromise, and sometimes we choose
> to compromise. I looked at the circuit of the M484 and I might not have the
> parts in the parts box...

I assume you mean M452 here, I can't find a reference to M484.

I suspect many of the parts are not that critical.

> .. its also a nasty hybrid design with DC biased NPN and PNP transistors. I
> find it ugly and can see it being a pig to debug, though it simulates fine
> in LTspice...

I didn't find it that hard to basically understand in my head. After all, there
are only 4 transistors, and 2 of those are just an output buffer. Quite
why having both NPN and PNP transistors makes it harder to understand
I do not know.

I will leave the flames about Spice and simulation packages in general for
another day.

-tony

Components Data Books

[Mattis Lind]

When repairing machines it is some times hard to find the data sheet for a
particular component.
Sometimes google hasn't been able to find the the data sheet for me.

My father worked in the electronics business for his entire career and kept
a lot of the data books that he received.

I have compiled a list of them, mostly for my self, so that I somewhat
easier would find what I look for.

I publish it here. If  you have searched everywhere (bitsavers , google
etc) and not got a decent hit and think that one of the data books in my
fathers archive would help I might be able to assist. No - I am not going
to scan entire books. But a few pages is OK. The latency might be high
since the archive is located 100 km away.

https://docs.google.com/spreadsheets/d/1fTfBDLxl40e2iNrbwLv1ZGgIaXvz_toyvfcIk4eVAbk/edit?usp=sharing

I will add more to the list as time passes. There are quite a big bunch of
data books left to do an inventory on.

/Mattis

Re: On the Emulation of TU58s

[Paul Koning]

> On Jun 16, 2015, at 12:10 PM, tony duell  wrote:
> 
>> 
>> As long as we're talking philosophy, what do y'all think about emulating the 
>> TU58 drive, vs. emulating the TU58 > *tape*?
>> 
>> I cannot properly express my opinion of that tape cartridge design even if I 
>> violate list rules about use of 
>> profanity. But the drive itself isn't all that bad, aside from not having 
>> enough motors to manipulate a 
>> well-designed tape cartridge mechanism.
> 
> The tape cartridge (along with QIC cartridges, etc) is an interesting design. 
> Of course the general problem is 
> to run the tape at constant linear speed past the head while winding it off 
> one reel onto the other. In general
> there have been 3 solutions to this.

Another solution is to avoid the problem entirely by not requiring constant 
linear speed.  That’s what DECtape (the real one) does.
> 
> One is to drive the tape itself using a capstan and maybe a pinch roller. 
> Then have the takeup spool
> driven too fast with a slipping clutch in-line. And a weak brake on the 
> supply spool. This of course is what
> was done in audio recorders (reel to reel and cassette), Video recorders 
> (ditto), etc.

Or a variant: drive the takeup reel with a controlled torque motor and no slip 
clutch.  I think professional grade tape decks may have been built that way.

paul

Re: On the Emulation of TU58s

[Ian S. King]

Mark, I've thought of that for my HP 9845, too.  Sure would be nice to
fabricate something that's flexible hardware that can be programmed for the
peculiarities of various implementations.  I'll put it on my list of things
to do once I'm done with my dissertation.  :-)

On Tue, Jun 16, 2015 at 4:21 PM, Paul Koning  wrote:

>
> > On Jun 16, 2015, at 12:10 PM, tony duell 
> wrote:
> >
> >>
> >> As long as we're talking philosophy, what do y'all think about
> emulating the TU58 drive, vs. emulating the TU58 > *tape*?
> >>
> >> I cannot properly express my opinion of that tape cartridge design even
> if I violate list rules about use of
> >> profanity. But the drive itself isn't all that bad, aside from not
> having enough motors to manipulate a
> >> well-designed tape cartridge mechanism.
> >
> > The tape cartridge (along with QIC cartridges, etc) is an interesting
> design. Of course the general problem is
> > to run the tape at constant linear speed past the head while winding it
> off one reel onto the other. In general
> > there have been 3 solutions to this.
>
> Another solution is to avoid the problem entirely by not requiring
> constant linear speed.  That’s what DECtape (the real one) does.
> >
> > One is to drive the tape itself using a capstan and maybe a pinch
> roller. Then have the takeup spool
> > driven too fast with a slipping clutch in-line. And a weak brake on the
> supply spool. This of course is what
> > was done in audio recorders (reel to reel and cassette), Video recorders
> (ditto), etc.
>
> Or a variant: drive the takeup reel with a controlled torque motor and no
> slip clutch.  I think professional grade tape decks may have been built
> that way.
>
> paul
>
>


-- 
Ian S. King, MSIS, MSCS, Ph.D. Candidate
The Information School 

Archivist, Voices From the Rwanda Tribunal 
Value Sensitive Design Research Lab 

University of Washington

There is an old Vulcan saying: "Only Nixon could go to China."

Re: using new technology on old machines

[Noel Chiappa]

> From: wulfman

> 2.47 per each ic is kinda expensive

US$170 / 420 ICs = US$.40 per IC? (I suspect you swapped the numerator and
demoninator: 420 / 170 = 2.47.)

Seems not too unreasonable. I did order one, we'll see what it looks like
(thanks to the OP for the tip).

> i have 10s of thousands of each 74 series part there was ever made been
> collecting on ebay for 15 years

Want to get rid of some of the excess? :-)

Noel

Re: using new technology on old machines

[ben]

On 6/16/2015 9:58 AM, Pontus Pihlgren wrote:

On Tue, Jun 16, 2015 at 01:54:56PM +, tony duell wrote:


I find it odd that people want to have a lights-and-switches panel, but are 
prepared to totally
adulterate the hardware of the machine that drives it.



Are you honestly suggesting that I should rebuild a PDP-11/70
from things I have in my partsbin?

'cause that is what it sounds like.

/P



I was more expecting a PDP 8 :)
Ben.

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 18:21, Paul Koning wrote:



On Jun 16, 2015, at 12:10 PM, tony duell  wrote:



As long as we're talking philosophy, what do y'all think about emulating the TU58 
drive, vs. emulating the TU58 > *tape*?

I cannot properly express my opinion of that tape cartridge design even if I 
violate list rules about use of
profanity. But the drive itself isn't all that bad, aside from not having 
enough motors to manipulate a
well-designed tape cartridge mechanism.


The tape cartridge (along with QIC cartridges, etc) is an interesting design. 
Of course the general problem is
to run the tape at constant linear speed past the head while winding it off one 
reel onto the other. In general
there have been 3 solutions to this.


Another solution is to avoid the problem entirely by not requiring constant 
linear speed.  That’s what DECtape (the real one) does.


And yet another (possibly the most common one on computers) is to have a 
small drive wheel that pulls the tape at constant speed across the 
heads, and then have some other construction that drives the tape reels 
depending on tape tension or length. Think vacuum columns or spring 
loaded arms.


And then we have drives like the TU80/TU81 which do not seem to fit into 
any of the mentioned categories. I'm not entirely sure how they work, 
but I think they are similar to the DECtape in this sense.


Johnny

RE: On the Emulation of TU58s

[tony duell]

[Driving tape]

> Another solution is to avoid the problem entirely by not requiring constant 
> linear speed.  That’s what DECtape 
> (the real one) does.

Sure. A number of tape drives were built that way, the HP9865 (and thus the 
built-in tape drive on the
HP9830) is another example. 

>
> > One is to drive the tape itself using a capstan and maybe a pinch roller. 
> > Then have the takeup spool
> > driven too fast with a slipping clutch in-line. And a weak brake on the 
> > supply spool. This of course is what
> > was done in audio recorders (reel to reel and cassette), Video recorders 
> > (ditto), etc.
> 
> Or a variant: drive the takeup reel with a controlled torque motor and no 
> slip clutch.  I think professional grade > tape decks may have been built 
> that way.

They were. Or at least some semi-professional audio recorders were built like 
that. The Revox G36 (736) and Brennell Mk 5 among them (I happen to have both). 
Actually, the Philips V2000 video recorders (home machines,
not professional but quite the best of the home systems) did that. They had a 
pair of DC motors to directly
drive the 2 spools along with the capstan and head drum motors. No slipping 
clutches. Back tension was 
provided not by a light brake on the supply spool but by a suitable current 
through the supply spool motor
in those machines.

-tony

Re: On the Emulation of TU58s

[Mark J. Blair]

> On Jun 16, 2015, at 09:10 , tony duell  wrote:
> You would, of course, not know which track it was reading, so you would have 
> to output 2 blocks, one on
> each track, at once. And how would you detect it was writing? Look for an 
> extra signal at the coupling head
> or something?

That seems to me like it would be the trickiest part. The TU58 schematic 
appears to indicate that there are separate erase head gaps (not on a separate 
head like in audio cassette drives), so maybe those could be monitored to 
detect when a track is being written? Of course, that probably means that a 
custom 4-gap head would need to be made with gaps matching the two read/write 
and two erase gaps (and a concave surface, too, rather than recycling some 
audio tape head with suitable geometry to line up with just the read/write gaps.




-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

RE: On the Emulation of TU58s

[tony duell]

> That seems to me like it would be the trickiest part. The TU58 schematic 
> appears to indicate that there are 

I think so. Of course you could cheat by making it a read-only tape. But I 
don't like that.

> separate erase head gaps (not on a separate head like in audio cassette 
> drives), so maybe those could be 

I am pretty sure there is just one physical head on the TU58 drive chassis. So 
if there is a separate erase
field, it is a second gap in that head.

> monitored to detect when a track is being written? Of course, that probably 
> means that a custom 4-gap head 
> would need to be made with gaps matching the two read/write and two erase 
> gaps (and a concave surface, 
> too, rather than recycling some audio tape head with suitable geometry to 
> line up with just the read/write gaps.

Ouch. Good luck in getting that, and even more luck in getting it positioned 
properly!

-tony

RE: On the Emulation of TU58s

[tony duell]

> And yet another (possibly the most common one on computers) is to have a
> small drive wheel that pulls the tape at constant speed across the
> heads, and then have some other construction that drives the tape reels
> depending on tape tension or length. Think vacuum columns or spring
> loaded arms.

That is closely related to the capstan and weakly-driven take up spool I think.

> And then we have drives like the TU80/TU81 which do not seem to fit into
> any of the mentioned categories. I'm not entirely sure how they work,
> but I think they are similar to the DECtape in this sense.

I don't know. I can think of several ways it could work

1) There is a tacho on an arm that rests against the takeup spool (as in the 
Cipher F880). The control
system drives the spools to keep that speed constant.

2) Similar, but the tacho is a rotating tape guide that the tape goes round

3) It assumes the takeup spool is intially empty. It then drives forwards, and 
measures the 
speed of the supply spool. From that, you can work out the diameter of the 
supply spool, and
thus I guess the amount of tape. You can then (a) determine where you are on 
the tape by the
relative speed of the 2 spools, this gives you the amount of tape on the takeup 
spool and thus
how fast you need to turn that to get the right speed. 

One of my VHS video recorders does something similar to work out how much 
recording space is 
left on the cassette. 

-tony

Re: On the Emulation of TU58s

[Henk Gooijen]

-Oorspronkelijk bericht- 
From: Johnny Billquist 
Sent: Tuesday, June 16, 2015 7:31 PM 
To: cctalk@classiccmp.org 
Subject: Re: On the Emulation of TU58s 


[... snip ...]
And then we have drives like the TU80/TU81 which do not seem to fit into 
any of the mentioned categories. I'm not entirely sure how they work, 
but I think they are similar to the DECtape in this sense.


Johnny

-
The round (approx 2" diameter) "bearings" of the TU80 do not rotate.
Instead, the metal has tiny holes. Air pressure pushes the tape away
from the bearings. As the tape moves, due to movement pressure, the
tape comes closer to the air bearing. That is measured. To get the
air pressure back to some sort of equilibrium the pickup or supply
reel speed is adjusted.
That is how I understand the mechanism ... now writing this down, I
think I should read up the Theory of Operation chapter ...

- Henk

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 19:51, tony duell wrote:



And yet another (possibly the most common one on computers) is to have a
small drive wheel that pulls the tape at constant speed across the
heads, and then have some other construction that drives the tape reels
depending on tape tension or length. Think vacuum columns or spring
loaded arms.


That is closely related to the capstan and weakly-driven take up spool I think.


I would disagree. There is no slipping clutch. Instead, the motors (on 
both sides) are driven by the uptake available. When there is too 
little, the motors run to give out some more tape. When there is too 
much, the motors run to pick up the excess.


So, motors can actually run in both directions, as needed. They are 
actually controlled by a pretty dumb closed loop system.


The actual tape movement as such, is all done by the small wheel next to 
the head, which just runs the tape past the head.



And then we have drives like the TU80/TU81 which do not seem to fit into
any of the mentioned categories. I'm not entirely sure how they work,
but I think they are similar to the DECtape in this sense.


I don't know. I can think of several ways it could work


I can also think of several. I just don't know for sure what it does.


1) There is a tacho on an arm that rests against the takeup spool (as in the 
Cipher F880). The control
system drives the spools to keep that speed constant.


There can definitely be a tacho on the motor, but since you do not know 
how much tape is on the reel, this will actually not tell you the tape 
speed. But there is no tacho on the tape itself, unless my memory fails me.



2) Similar, but the tacho is a rotating tape guide that the tape goes round


See above.


3) It assumes the takeup spool is intially empty. It then drives forwards, and 
measures the
speed of the supply spool. From that, you can work out the diameter of the 
supply spool, and
thus I guess the amount of tape. You can then (a) determine where you are on 
the tape by the
relative speed of the 2 spools, this gives you the amount of tape on the takeup 
spool and thus
how fast you need to turn that to get the right speed.


That would be very hard, as you do not know the thickness of the tape, 
nor the diameter of the tape reel center.


I've been wondering if there is some sensor of tape tension/pressure at 
the heads, and this will allow the drive to figure out how much 
faster/slower the reels must run, relative to each other, in order to 
keep the tape tensioned. Then you can figure out tape speed across the 
heads (if you care) by just observing flux changes.



One of my VHS video recorders does something similar to work out how much 
recording space is
left on the cassette.


That can't be very precise... :-)

Johnny

Re: On the Emulation of TU58s

[Mark J. Blair]

> On Jun 16, 2015, at 10:54 , tony duell  wrote:
> I am pretty sure there is just one physical head on the TU58 drive chassis. 
> So if there is a separate erase
> field, it is a second gap in that head.

Correct. Single head with multiple gaps.

> 
> Ouch. Good luck in getting that, and even more luck in getting it positioned 
> properly!

Yup! That's why I'm presenting this as a philosophical debate, rather than 
something even crazy old me would think of building! :)

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: On the Emulation of TU58s

[Chuck Guzis]

On 06/16/2015 11:08 AM, Henk Gooijen wrote:


The round (approx 2" diameter) "bearings" of the TU80 do not rotate.
Instead, the metal has tiny holes. Air pressure pushes the tape away
from the bearings. As the tape moves, due to movement pressure, the
tape comes closer to the air bearing. That is measured. To get the
air pressure back to some sort of equilibrium the pickup or supply
reel speed is adjusted.
That is how I understand the mechanism ... now writing this down, I
think I should read up the Theory of Operation chapter ...


Pretty much the standard CDC vacuum-column design since the 1960s.  The 
TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape 
movement is determined by applying positive or negative pressure to 
ether or both (i.e. positive pressure on both results in the tape "floating"


--Chuck

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 20:20, Chuck Guzis wrote:

On 06/16/2015 11:08 AM, Henk Gooijen wrote:


The round (approx 2" diameter) "bearings" of the TU80 do not rotate.
Instead, the metal has tiny holes. Air pressure pushes the tape away
from the bearings. As the tape moves, due to movement pressure, the
tape comes closer to the air bearing. That is measured. To get the
air pressure back to some sort of equilibrium the pickup or supply
reel speed is adjusted.
That is how I understand the mechanism ... now writing this down, I
think I should read up the Theory of Operation chapter ...


Pretty much the standard CDC vacuum-column design since the 1960s.  The
TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape
movement is determined by applying positive or negative pressure to
ether or both (i.e. positive pressure on both results in the tape
"floating"


Uh... The TU80/TU81 do not have vacuum columns...

Johnny

Re: On the Emulation of TU58s

[Mark J. Blair]

> On Jun 16, 2015, at 11:22 , Johnny Billquist  wrote:
>> 
>> Pretty much the standard CDC vacuum-column design since the 1960s.  The
>> TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape
>> movement is determined by applying positive or negative pressure to
>> ether or both (i.e. positive pressure on both results in the tape
>> "floating"
> 
> Uh... The TU80/TU81 do not have vacuum columns...

Or rotating capstans...


-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: On the Emulation of TU58s

[Chuck Guzis]

On 06/16/2015 11:22 AM, Johnny Billquist wrote:


Uh... The TU80/TU81 do not have vacuum columns...


I didn't say that they did, Johnny.  I said that the TU80 hails back to 
the vacuum-column CDC drive design of the 1960s.  At least that's my 
understanding.


--Chuck

Re: On the Emulation of TU58s

[Henk Gooijen]

-Oorspronkelijk bericht- 
From: Johnny Billquist 
Sent: Tuesday, June 16, 2015 8:22 PM 
To: cctalk@classiccmp.org 
Subject: Re: On the Emulation of TU58s 


On 2015-06-16 20:20, Chuck Guzis wrote:

On 06/16/2015 11:08 AM, Henk Gooijen wrote:


The round (approx 2" diameter) "bearings" of the TU80 do not rotate.
Instead, the metal has tiny holes. Air pressure pushes the tape away
from the bearings. As the tape moves, due to movement pressure, the
tape comes closer to the air bearing. That is measured. To get the
air pressure back to some sort of equilibrium the pickup or supply
reel speed is adjusted.
That is how I understand the mechanism ... now writing this down, I
think I should read up the Theory of Operation chapter ...


Pretty much the standard CDC vacuum-column design since the 1960s.  The
TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape
movement is determined by applying positive or negative pressure to
ether or both (i.e. positive pressure on both results in the tape
"floating"


Uh... The TU80/TU81 do not have vacuum columns...

Johnny

-
well, the tiny space between the tape and the air bearing could
be regarded a vacuum column, but it's a very short one :-)
The two air bearings are immediately above and below the R/W
and erase head. And they do *not* rotate. The tape glides on
an air cushion over the bearing.

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 20:23, Mark J. Blair wrote:



On Jun 16, 2015, at 11:22 , Johnny Billquist  wrote:


Pretty much the standard CDC vacuum-column design since the 1960s.  The
TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape
movement is determined by applying positive or negative pressure to
ether or both (i.e. positive pressure on both results in the tape
"floating"


Uh... The TU80/TU81 do not have vacuum columns...


Or rotating capstans...


Bu the way. For the vacuum column drives that I know 
(TU16/TU45/TU77/TU78), tape movement is not determined by vacuum as such.


Each column have about 8 pressure switches. When 4 have low pressure, 
and 4 have atmospheric pressure, the drive is happey, and the reels are 
resting. When the point of underpressure/pressure moves down, the reel 
on that side starts moving to pick up more tape, thus moving the point 
back towards neutral. When the point moves up, the reel starts moving to 
give out more tape, to move the point back down again. The more switches 
triggered in either direction, the faster the reel will move.


The movement of the tape across the head is controlled by a third motor, 
which have a smaller wheel on it. The tape lies against this reel, but 
it's all done by friction. This wheel pretty much runs the tape across 
the head at constant speed, and this movement of the tape will also 
cause the points in the two columns to move, which in turn will trigger 
action as described in the previous section.


Not sure where the counter-rotating capstans would fit into this either...
And there is only negative pressure, and it is applied to the tape at 
all time.


Johnny

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 20:28, Chuck Guzis wrote:

On 06/16/2015 11:22 AM, Johnny Billquist wrote:


Uh... The TU80/TU81 do not have vacuum columns...


I didn't say that they did, Johnny.  I said that the TU80 hails back to
the vacuum-column CDC drive design of the 1960s.  At least that's my
understanding.


But I can't see any relationship between vacuum column tape drives and 
how the TU80/TU81 works. You'll have to explain this to me in way more 
detail, because right now, you have totally lost me. :-)


Johnny

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 20:30, Henk Gooijen wrote:

-Oorspronkelijk bericht- From: Johnny Billquist Sent: Tuesday,
June 16, 2015 8:22 PM To: cctalk@classiccmp.org Subject: Re: On the
Emulation of TU58s
On 2015-06-16 20:20, Chuck Guzis wrote:

On 06/16/2015 11:08 AM, Henk Gooijen wrote:


The round (approx 2" diameter) "bearings" of the TU80 do not rotate.
Instead, the metal has tiny holes. Air pressure pushes the tape away
from the bearings. As the tape moves, due to movement pressure, the
tape comes closer to the air bearing. That is measured. To get the
air pressure back to some sort of equilibrium the pickup or supply
reel speed is adjusted.
That is how I understand the mechanism ... now writing this down, I
think I should read up the Theory of Operation chapter ...


Pretty much the standard CDC vacuum-column design since the 1960s.  The
TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape
movement is determined by applying positive or negative pressure to
ether or both (i.e. positive pressure on both results in the tape
"floating"


Uh... The TU80/TU81 do not have vacuum columns...

Johnny

-
well, the tiny space between the tape and the air bearing could
be regarded a vacuum column, but it's a very short one :-)
The two air bearings are immediately above and below the R/W
and erase head. And they do *not* rotate. The tape glides on
an air cushion over the bearing.


Hmm, I guess it could. But it is a very different construct compared to 
a vacuum column drive. In this case we're talking about overpressure to 
act as a cushion, and not underpressure to act as a takeup/buffer mechanism.


Johnny

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 20:34, Johnny Billquist wrote:

On 2015-06-16 20:30, Henk Gooijen wrote:

-Oorspronkelijk bericht- From: Johnny Billquist Sent: Tuesday,
June 16, 2015 8:22 PM To: cctalk@classiccmp.org Subject: Re: On the
Emulation of TU58s
On 2015-06-16 20:20, Chuck Guzis wrote:

On 06/16/2015 11:08 AM, Henk Gooijen wrote:


The round (approx 2" diameter) "bearings" of the TU80 do not rotate.
Instead, the metal has tiny holes. Air pressure pushes the tape away
from the bearings. As the tape moves, due to movement pressure, the
tape comes closer to the air bearing. That is measured. To get the
air pressure back to some sort of equilibrium the pickup or supply
reel speed is adjusted.
That is how I understand the mechanism ... now writing this down, I
think I should read up the Theory of Operation chapter ...


Pretty much the standard CDC vacuum-column design since the 1960s.  The
TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape
movement is determined by applying positive or negative pressure to
ether or both (i.e. positive pressure on both results in the tape
"floating"


Uh... The TU80/TU81 do not have vacuum columns...

Johnny

-
well, the tiny space between the tape and the air bearing could
be regarded a vacuum column, but it's a very short one :-)
The two air bearings are immediately above and below the R/W
and erase head. And they do *not* rotate. The tape glides on
an air cushion over the bearing.


Hmm, I guess it could. But it is a very different construct compared to
a vacuum column drive. In this case we're talking about overpressure to
act as a cushion, and not underpressure to act as a takeup/buffer
mechanism.


So I decided to read up on the TU81 operation, and it does work by 
creating an overpressure to act as a bearing before and after the head.
The overpressure is also used to detect tape tension so that a constant 
tension can be maintained.
The supply reel is controlled by the air pressure sensors, so that 
tension is maintained, while the pickup reel is directly controlling the 
speed. Both reels have tachos as well.
There is no capstan, but constant linear speed can be maintained by the 
fact that the takeup reel is of a known size, and you have the tachos, 
and you essentially can estimate good enough how much tape is on the 
takeup reel.

(Lots of computations in here... :-) )

Johnny

RE: On the Emulation of TU58s

[tony duell]

> >
> >> And yet another (possibly the most common one on computers) is to have a
> >> small drive wheel that pulls the tape at constant speed across the
> >> heads, and then have some other construction that drives the tape reels
> >> depending on tape tension or length. Think vacuum columns or spring
> >> loaded arms.
> >
> > That is closely related to the capstan and weakly-driven take up spool I 
> > think.
> 
> I would disagree. There is no slipping clutch. Instead, the motors (on

True. I meant it was a system where the tape speed was determined by the
capstan, and the reels are driven to keep the tape round up, not all over the 
machine room floor :-)

> The actual tape movement as such, is all done by the small wheel next to
> the head, which just runs the tape past the head.

Which is essentailly the same as the capstan in an audio tape recorder, albeit 
the computer
drive doesn't have a pinch roller

> I've been wondering if there is some sensor of tape tension/pressure at
> the heads, and this will allow the drive to figure out how much
> faster/slower the reels must run, relative to each other, in order to
> keep the tape tensioned. Then you can figure out tape speed across the
> heads (if you care) by just observing flux changes.

Only if there is something on the tape. These computer tape drives could surely 
record on a 
totally blank tape and get the right number of bits per inch. So the thing 
can't use the data rate
at the head as a speed measurement.

> > One of my VHS video recorders does something similar to work out how much 
> > recording space is
> > left on the cassette.
> 
> That can't be very precise... :-)

It always underestimates the remaining tape (so that if it says there is 1 hour 
left, you can definitely fit
a 1 hour TV programme on there). But it is suprisingly good. 

-tony

RE: using new technology on old machines. Was: PDP-12 Restoration at the RICM

[Fred Cisin]

On Tue, 16 Jun 2015, tony duell wrote:

Actually, IIRC a USB A male->female cable violates the spec...


The spec forbids extending the cable further?


Or should the spec forbid absolutely any cable,
with absolutely any USB connector on either end?

Re: On the Emulation of TU58s

[Paul Koning]

> On Jun 16, 2015, at 3:20 PM, tony duell  wrote:
> 
> ...
>> The actual tape movement as such, is all done by the small wheel next to
>> the head, which just runs the tape past the head.
> 
> Which is essentailly the same as the capstan in an audio tape recorder, 
> albeit the computer
> drive doesn't have a pinch roller

Most don’t.  Some do.  I remember using IBM tape drives on a 360 Model 44 that 
were amazingly badly designed.

Part 1: two capstans spinning all the time, in opposite directions.  
Solenoid-activated pinch rollers would press the tape against the capstan to 
set it moving.  The same solenoid-activated pinch roller moved in the opposite 
direction would press the tape against a non-moving “capstan" to stop it.

Part 2: vacuum columns — no surprise there.  But why on earth would anyone 
build a vacuum column that has the oxide side of the tape facing OUTward, 
rubbing the oxide against the column side walls?

Amazingly enough, those drives did work reasonably reliably, but I would never 
want such a beast in my shop.

paul

RE: using new technology on old machines

[Fred Cisin]

On Tue, 16 Jun 2015, tony duell wrote:
Quite probably, but the modern mains-side switcher is more 
troublesome and a lot less pleasant to repair. I think I'll stick

with the room-heater in my 11's :-)


Well, you could use a switcher, paralleled to the mains with a heater.
Just as you can use a CFL along with a heater for some applications
that call for an incandescent.

Re: On the Emulation of TU58s

[Mark J. Blair]

> On Jun 16, 2015, at 12:31 , Paul Koning  wrote:
> Part 1: two capstans spinning all the time, in opposite directions.  
> Solenoid-activated pinch rollers would press the tape against the capstan to 
> set it moving.

That's also how the magnetic card is moved in and out in the Mag Card II 
typewriter. There's a pair of counter-rotating capstan wheels below the card, 
and a pair of solenoid-actuated pinch rollers opposite them, above the card. 
The head is moved from track to track with a solenoid-actuated escapement that 
lets the head move one track at a time under spring pressure, and then yet 
another clutch lets a free-running roller grab a cable to pull the head back to 
the first track.

I have one waiting for my attention. I think the job will be much more 
mechanical than electronic!

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

RE: using new technology on old machines

[tony duell]

> > Quite probably, but the modern mains-side switcher is more
> > troublesome and a lot less pleasant to repair. I think I'll stick
> > with the room-heater in my 11's :-)
> 
> Well, you could use a switcher, paralleled to the mains with a heater.

One reason I want to keep the original supplies in my 11's is that they are 
a lot easier to keep going than a mains-side swticher. Yes, they are 
switchign regulators, but the chopper works at 30V or so, on the output
side of a big iron-core mains transformer. So no lethal voltage around.

Using a mains-side switcher in parallel with a heating element would 
seem to be the worst of both worlds.

Actually, no. That honour goes to the PSU in a Zenith MDA monitor
which as I said 'combines the efficiency of a linear with the reliability
of a switcher'. The design (if you can call it that) of this PSU is to
rectify the mains, feed it into a free-running chopper circuit, then
a transformer. The output of that is half-wave (!) rectified giving
about 18V DC. Note the chopper free-runs, so there is no regulation
applied at this point. That 18V is then fed to a discrete-transistor
linear regulator.  

And that's not the end of the 'curious' design. As you know, a linear
regualtor compares the output voltage of the supply with a
reference votlage. That reference voltage is typically produced by
a zener diode. Not in this monitor. It uses the drop across the 
power-on LED. Which means it is important to use a green LED. 
Another colour, with a different Vf, and the PSU output is wrong.



> Just as you can use a CFL along with a heater for some applications
> that call for an incandescent.

I once saw a curious lightbulb which contained both a mercury vapour 
discharge lamp and a filament. The idea was that the latter would
provide some red light to go along with the predominantly 
blue/green mercury lamp. I think the filament was also the ballast
for the dischage lamp.

Oh well.. The time I need a filament lamp is when I am using it for
the electrical characteristics (e.g. using it as a ballast resistor),
so no kludge with a CFL is likely to work

-tony

RE: On the Emulation of TU58s

[tony duell]

> > On Jun 16, 2015, at 12:31 , Paul Koning  wrote:
> > Part 1: two capstans spinning all the time, in opposite directions.  
> > Solenoid-activated pinch rollers would
> > press  the tape against the capstan to set it moving.

> That's also how the magnetic card is moved in and out in the Mag Card II 
> typewriter. There's a pair of counter-
> rotating capstan wheels below the card, and a pair of solenoid-actuated pinch 
> rollers opposite them, above the 

And how the paper tape is moved in a Trend HSR500 reader. 2 capstans, one each 
side of the read head
and 2 solenoid-operated pinch rollers under them. And an electromagnet and 
armature as a brake.

For something even madder, look at the design of the original Radio Shack 'Line 
Printer' which was
actually a Centronics something-pr-other (733?). This thing (which is not a 
line printer at all) has a belt 
running across the chassis with a motor continuously driving it (a shaded pole 
motor I think). Solenoids 
on the printhead carriage grab the top or bottom run of the belt depending on 
which way the carriage 
is to move.

-tony

Re: On the Emulation of TU58s

[Eric Smith]

Johnny Billquist wrote:
> Then you can figure out tape speed across the
> heads (if you care) by just observing flux changes.

Tony Duell wrote:
> Only if there is something on the tape. These computer tape drives could 
> surely record on a
> totally blank tape and get the right number of bits per inch. So the thing 
> can't use the data rate
> at the head as a speed measurement.

Not for something that can write a blank tape (e.g. a 7-track or
9-track), but there were other tape systems that required a formatted
tape, and servoed the reel motors to the flux transition rate.
Obviously the factory had to use a drive with a different tape speed
control system to format the tape.

Re: On the Emulation of TU58s

[Mark J. Blair]

> On Jun 16, 2015, at 12:46 , tony duell  wrote:
> For something even madder, look at the design of the original Radio Shack 
> 'Line Printer' which was
> actually a Centronics something-pr-other (733?). This thing (which is not a 
> line printer at all) has a belt 
> running across the chassis with a motor continuously driving it (a shaded 
> pole motor I think). Solenoids 
> on the printhead carriage grab the top or bottom run of the belt depending on 
> which way the carriage 
> is to move.

Is that the same screwball printer that has a metal platen spinning behind the 
paper with horizontal raised lines on it, and a single vertical striker in the 
printhead that strikes at the moment when the platen and striker intersect at 
the desired X/Y location of the dot to be printed? I've considered buying one 
just to hear what it sounds like.


-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

RE: On the Emulation of TU58s

[tony duell]

[Centronics belt-grabbing printer]


> Is that the same screwball printer that has a metal platen spinning behind 
> the paper with horizontal raised lines on 
> it, and a single vertical striker in the printhead that strikes at the moment 
> when the platen and striker intersect at 
> the desired X/Y location of the dot to be printed? I've considered buying one 
> just to hear what it sounds like.

No. That sounds like a Seikosha (?spel) Unihammer printer. Radio Shack sold it 
as the DMP110, I think
Amstrad and Commodore sold them too (probably with different firmware). From 
what I remember 
(I have a DMP110, but haven't used it for many years) they produce a fairly 
high-pitched buzz.

Then of course there is the Olivetti sparkjet printer. A really crazy thing 
that blasts solid toner from a 
rod of same by producing a spark from said rod to a fixed electrode. The toner 
doesn't all end up
on the electrode, some goes on the paper. Or at least that#s the idea. Setting 
one up is an interesting
job (I turned a pointed pin to make things a little easier) and the quality is 
non-existant even when it is
working properly.

-tony

Re: On the Emulation of TU58s

[Mark J. Blair]

> On Jun 16, 2015, at 09:10 , tony duell  wrote:
> 
> Incidentally, given the fact that a constant motor speed -> constant tape 
> speed, it should be possible to
> make a device to put the timing track on a blank tape for the TU58. Has 
> anyone done that?

There's no timing track in the TU58 scheme, but there are magnetic BOT and EOT 
markers that have to be written so that the drive can identify the tape ends. I 
assume there are also block headers much like on most floppy disks, but I 
haven't gotten that deep into the formatting yet.

The tape includes the BOT and EOT sensing punched holes, and the cartridge 
includes the angled mirror behind the tape to allow the holes to be sensed with 
a right-angled optical path. But the TU58-XA drive mechanism does not include 
the optical sensor that would be needed to sense tape ends on an unformatted 
tape. I don't know if this was meant as a way to further cost-reduce the 
already mechanically simple tape drive mechanism, or if DEC did that 
deliberately to make sure that non-DEC DC100/DC150 cartridges could not be be 
formatted in the field, so that users would be stuck buying preformatted 
cartridges from DEC.

If new cartridges with brand new, un-decayed belts could be manufactured, then 
it should be possible to hack up a TU58-XA mechanism for formatting them. I 
think there may be a little hole in the plastic casting of the drive where one 
of the optical sensors might be glued in place, if I recall correctly.

Oh yeah, the metal vs. plastic base cartridges were also mentioned in this 
thread. I've only encountered the metal ones so far. Based on the manual 
pictures, I think the plastic ones use a shorter belt with a simpler path.

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Re: On the Emulation of TU58s

[Chuck Guzis]

On 06/16/2015 11:30 AM, Henk Gooijen wrote:


well, the tiny space between the tape and the air bearing could
be regarded a vacuum column, but it's a very short one :-)
The two air bearings are immediately above and below the R/W
and erase head. And they do *not* rotate. The tape glides on
an air cushion over the bearing.


Yeah, a case of mental dyspepsia.

So do any post-1980s 1/2" open-reel tape drives employ vacuum columns? 
I was thinking of DG drive (about half-rack size) that I believe had 
them, but I"m not sure of the date of manufacture.


Does this apparent lack of start-stop on a dime drives have anything to 
do with the decline in tape as a working medium (as opposed to a backup 
or distribution medium)?  This is obvious when one looks at an OS such 
as UNIX or PRIMOS; the tape was treated as pretty much an archival device.


Used to be that either Flores or (later) Knuth on sort/merge operations 
was a standard on many a programmer's bookshelf.   Not so much, I 
gather, in the last couple of decades?


--Chuck

RE: using new technology on old machines

[Kyle Owen]

On Jun 16, 2015 3:43 PM, "tony duell"  wrote:
>
> Actually, no. That honour goes to the PSU in a Zenith MDA monitor
> which as I said 'combines the efficiency of a linear with the reliability
> of a switcher'. The design (if you can call it that) of this PSU is to
> rectify the mains, feed it into a free-running chopper circuit, then
> a transformer. The output of that is half-wave (!) rectified giving
> about 18V DC. Note the chopper free-runs, so there is no regulation
> applied at this point. That 18V is then fed to a discrete-transistor
> linear regulator.
>
> And that's not the end of the 'curious' design. As you know, a linear
> regualtor compares the output voltage of the supply with a
> reference votlage. That reference voltage is typically produced by
> a zener diode. Not in this monitor. It uses the drop across the
> power-on LED. Which means it is important to use a green LED.
> Another colour, with a different Vf, and the PSU output is wrong.
>

I would love to have a copy of that schematic for an Engineering Wall of
Shame. Seriously, that is the strangest supply design I've ever heard.

Kyle

Re: Components Data Books

[Sean Caron]

Mine too! I just love the old paper books versus PDFs ... and I've got a
pretty decent collection of databooks both that I have picked up second
hand, as well as a pretty large chunk of those that my dad acquired over
the course of his engineering career when he was cleaning them out from his
library ... I don't have quite so many ... probably not more than a hundred
in total ... mostly focused on digital but I've got a little bit of
everything; connectors; discrete components; analog; power; telecom; RF ...
if this sort of thing is useful to people, I'd be happy to pitch in with
the effort here, to cover requests for datasheets that aren't available
from the usual sources. I've got a few that might be a bit obscure.

Best,

Sean


On Tue, Jun 16, 2015 at 12:30 PM, Mattis Lind  wrote:

> When repairing machines it is some times hard to find the data sheet for a
> particular component.
> Sometimes google hasn't been able to find the the data sheet for me.
>
> My father worked in the electronics business for his entire career and kept
> a lot of the data books that he received.
>
> I have compiled a list of them, mostly for my self, so that I somewhat
> easier would find what I look for.
>
> I publish it here. If  you have searched everywhere (bitsavers , google
> etc) and not got a decent hit and think that one of the data books in my
> fathers archive would help I might be able to assist. No - I am not going
> to scan entire books. But a few pages is OK. The latency might be high
> since the archive is located 100 km away.
>
>
> https://docs.google.com/spreadsheets/d/1fTfBDLxl40e2iNrbwLv1ZGgIaXvz_toyvfcIk4eVAbk/edit?usp=sharing
>
> I will add more to the list as time passes. There are quite a big bunch of
> data books left to do an inventory on.
>
> /Mattis
>

Re: Components Data Books

[ben]

On 6/16/2015 12:01 PM, Sean Caron wrote:

Mine too! I just love the old paper books versus PDFs ... and I've got a
pretty decent collection of databooks both that I have picked up second
hand, as well as a pretty large chunk of those that my dad acquired over
the course of his engineering career when he was cleaning them out from his
library ... I don't have quite so many ... probably not more than a hundred
in total ... mostly focused on digital but I've got a little bit of
everything; connectors; discrete components; analog; power; telecom; RF ...
if this sort of thing is useful to people, I'd be happy to pitch in with
the effort here, to cover requests for datasheets that aren't available
from the usual sources. I've got a few that might be a bit obscure.

Best,

Sean

I love old books too, but I have no more space in my apartment.
Ben.

Re: Components Data Books

[Dale H. Cook]

At 12:30 PM 6/16/2015, Mattis Lind wrote:

>I have compiled a list of them, mostly for my self, so that I somewhat easier 
>would find what I look for.

That is a nice list, and includes many that are not among my ~80 (which does 
not include my ~60 vacuum tube manuals). Could you post the original 
spreadsheet somewhere? It would be a reference that would be much easier to use 
than the online version.

Dale H. Cook, Roanoke/Lynchburg, VA
Osborne 1 / Kaypro 4-84 / Kaypro 1 / Amstrad PPC-640
http://plymouthcolony.net/starcity/radios/index.html 

Re: On the Emulation of TU58s

[Brent Hilpert]

On 2015-Jun-16, at 12:31 PM, Paul Koning wrote:
>> On Jun 16, 2015, at 3:20 PM, tony duell  wrote:
>> ...
>>> The actual tape movement as such, is all done by the small wheel next to
>>> the head, which just runs the tape past the head.
>> 
>> Which is essentailly the same as the capstan in an audio tape recorder, 
>> albeit the computer
>> drive doesn't have a pinch roller
> 
> Most don’t.  Some do.  I remember using IBM tape drives on a 360 Model 44 
> that were amazingly badly designed.

Once ran across a Honeywell drive (7-track) that had a 'vacuum capstan'. The 
capstan wheel had a vacuum path through the axle and then transferred the 
vacuum out to holes around the perimeter. So rather than a pinch roller or 
rubber frictional surface on the capstan to grip the tape, it was a vacuum 
holding the tape to the smooth metal surface of the rotating capstan.  Or was 
this common on higher-end vac-column drives?

Re: On the Emulation of TU58s

[Johnny Billquist]

On 2015-06-16 21:20, tony duell wrote:



And yet another (possibly the most common one on computers) is to have a
small drive wheel that pulls the tape at constant speed across the
heads, and then have some other construction that drives the tape reels
depending on tape tension or length. Think vacuum columns or spring
loaded arms.


That is closely related to the capstan and weakly-driven take up spool I think.


I would disagree. There is no slipping clutch. Instead, the motors (on


True. I meant it was a system where the tape speed was determined by the
capstan, and the reels are driven to keep the tape round up, not all over the
machine room floor :-)


Ok. Then I would agree. :-)


The actual tape movement as such, is all done by the small wheel next to
the head, which just runs the tape past the head.


Which is essentailly the same as the capstan in an audio tape recorder, albeit 
the computer
drive doesn't have a pinch roller


Right.


I've been wondering if there is some sensor of tape tension/pressure at
the heads, and this will allow the drive to figure out how much
faster/slower the reels must run, relative to each other, in order to
keep the tape tensioned. Then you can figure out tape speed across the
heads (if you care) by just observing flux changes.


Only if there is something on the tape. These computer tape drives could surely 
record on a
totally blank tape and get the right number of bits per inch. So the thing 
can't use the data rate
at the head as a speed measurement.


Ah... Good point. I didn't even think about writing. Stupid of me. :-)
Anyway, it seems the drive do some clever computations to figure out how 
to keep the speed constant.


Johnny

--
Johnny Billquist  || "I'm on a bus
  ||  on a psychedelic trip
email: b...@softjar.se ||  Reading murder books
pdp is alive! ||  tryin' to stay hip" - B. Idol

Re: On the Emulation of TU58s

[Chuck Guzis]

On 06/16/2015 01:54 PM, Brent Hilpert wrote:


Once ran across a Honeywell drive (7-track) that had a 'vacuum
capstan'. The capstan wheel had a vacuum path through the axle and
then transferred the vacuum out to holes around the perimeter. So
rather than a pinch roller or rubber frictional surface on the
capstan to grip the tape, it was a vacuum holding the tape to the
smooth metal surface of the rotating capstan.  Or was this common on
higher-end vac-column drives?


Two counter-rotating capstans on the CDC 60x, 65x, 66x drives at least. 
 The vacuum/pressure was switched by means of a voice-coil valve.  IBM 
seemed wedded to the pinch-roller model.


I can recall having a discussion about who had the "sloppy write/careful 
read" versus the "careful write/sloppy read" technology, but don't 
recall who claimed which.  I do remember hours spent with various tapes, 
developer (e.g. Magna-see) and a loupe looking at patterns on problem tapes.


--Chuck

RE: using new technology on old machines

[Dave G4UGM]

> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of tony
duell
> Sent: 16 June 2015 17:29
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: RE: using new technology on old machines
> 
> 
> > > It's also that this is the 'classic computers' list. To me, classic
> > > computing means rather more than just the hardware. It also covers
> > > the design and construction methods, technology and so on. And there
> > > seems to be precious little of that in a modern microcontroller
> > > acting as a clock oscillator.
> >
> >
> > There isn't., but some-times we have to compromise, and sometimes we
> > choose to compromise. I looked at the circuit of the M484 and I might
> > not have the parts in the parts box...
> 
> I assume you mean M452 here, I can't find a reference to M484.

I did don't know where 484 came from

> 
> I suspect many of the parts are not that critical.
> 

I don't think so either, but I see from:-

http://dustyoldcomputers.com/pdp-common/reference/drawings/modules/m/m452.pd
f

that the original appears to use a 2k 10-turn pot, and a 7440 output buffer,
neither of which are in my rather extensive junk box.
In fact the 7440 are rather rare, and I see the cheapest I can get them for
is around $4.00 each.

I do however have a tube of pic 16f84 chips and a few 4Mhz crystals and so
could build a suitable generator with 1 x IC and 1 xtal.

The great thing about PIC, Arduino and FPGA is they allow the creation of
something which is as functionally identical to the original as you can get
without duplicating it. 

> > .. its also a nasty hybrid design with DC biased NPN and PNP
> > transistors. I find it ugly and can see it being a pig to debug,
> > though it simulates fine in LTspice...
> 
> I didn't find it that hard to basically understand in my head. After all,
there
> are only 4 transistors, and 2 of those are just an output buffer. Quite
why
> having both NPN and PNP transistors makes it harder to understand I do not
> know.

I am really used to RF circuits so am puzzled there is no inductor. It kind
of looks like a Darlington Pair but it isn't.
What I don't understand is why the emitter of Q1 is spliced in what I assume
is a voltage divider in the collector of q2.
I was expecting a multivibrator circuit...


> 
> I will leave the flames about Spice and simulation packages in general for
> another day.

You are touchy. Would it help if I used the original Spice2 written in
Fortran IV. It still works. Sadly I don't have a real mainframe but have to
use Hercules to run it

> 
> -tony

Dave

Re: using new technology on old machines

[Paul Koning]

> On Jun 16, 2015, at 4:05 PM, Kyle Owen  wrote:
> 
> On Jun 16, 2015 3:43 PM, "tony duell"  wrote:
>> 
>> Actually, no. That honour goes to the PSU in a Zenith MDA monitor
>> which as I said 'combines the efficiency of a linear with the reliability
>> of a switcher'. The design (if you can call it that) of this PSU is to
>> rectify the mains, feed it into a free-running chopper circuit, then
>> a transformer. The output of that is half-wave (!) rectified giving
>> about 18V DC. Note the chopper free-runs, so there is no regulation
>> applied at this point. That 18V is then fed to a discrete-transistor
>> linear regulator.

Maybe someone learned how high voltage supplies for TV sets work (from the 
sweep voltage) and decided to apply that.  It does sound like someone with too 
little knowledge or ability for the job.

>> 
>> And that's not the end of the 'curious' design. As you know, a linear
>> regualtor compares the output voltage of the supply with a
>> reference votlage. That reference voltage is typically produced by
>> a zener diode. Not in this monitor. It uses the drop across the
>> power-on LED. Which means it is important to use a green LED.
>> Another colour, with a different Vf, and the PSU output is wrong.
>> 
> 
> I would love to have a copy of that schematic for an Engineering Wall of
> Shame. Seriously, that is the strangest supply design I've ever heard.

That doesn’t seem so bad.  Diodes have well defined forward drops, and it 
certainly is not unprecedented to use the forward drop of, say, a plain silicon 
rectifier as a reference, or as a fixed drop where that value is needed.  The 
same goes for LEDs.  Of course it depends on the material (band gap voltage) 
which means it depends on the color.  While this particular thing is a bit odd, 
it seems like a clever optimization, eliminating a part by having one that was 
wanted anyway do two jobs.  Sort of the hardware equivalent of reusing a 
instruction as a constant — which I understand was done in some PDP-8 device 
drivers (the DECtape driver comes to mind).

paul

Re: using new technology on old machines

[Mike Ross]

On Wed, Jun 17, 2015 at 1:54 AM, tony duell  wrote:

> It's also that this is the 'classic computers' list. To me, classic computing 
> means rather
> more than just the hardware. It also covers the design and construction 
> methods, technology
> and so on.

DING.

Staying slightly on-topic, working on serious wire-wrap backplanes can
get a bit hairy. We probably all have hand-wrapping tools, and can do
the occasional repair or patch as required. But...

'remanufacturing' has become part of preservation movements in
general; 'preservation/re-creation' might be a better name. The
ultimate example of this might be from the railway world. A famous
class of British steam locomotives - the A1 Pacific - had become
extinct; all were scrapped before railway preservation really became a
Big Thing. So, enough enthusiasts got together and they *built* one.
>From scratch, from raw metal: http://www.a1steam.com

There are various bits of DEC hardware that are extinct, or in
critically short supply. I would love to have a TC15 DECtape
controller for my pdp-15s; fat chance of ever finding one. Ditto for
memory for my KL10. Oh sure, we can make modern functionally
equivalent replacements, like Guy S, LCM etc, have done. But it's not
the same...

DEC backplanes were largely wire-wrapped by machine; I've seen
pictures. If the interest was there, it should be possible to restore
or re-create the machines used by DEC to manufacture backplanes. From
there, it's a relatively small step to source, or manufacture new
batches of, the modules etc. needed to populate them

Has this ever been seriously considered, or mooted as a possible
co-operative venture for a group of us?

Mike

http://www.corestore.org
'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'

Re: On the Emulation of TU58s

[Paul Koning]

> On Jun 16, 2015, at 3:48 PM, Eric Smith  wrote:
> 
> Johnny Billquist wrote:
>> Then you can figure out tape speed across the
>> heads (if you care) by just observing flux changes.
> 
> Tony Duell wrote:
>> Only if there is something on the tape. These computer tape drives could 
>> surely record on a
>> totally blank tape and get the right number of bits per inch. So the thing 
>> can't use the data rate
>> at the head as a speed measurement.
> 
> Not for something that can write a blank tape (e.g. a 7-track or
> 9-track), but there were other tape systems that required a formatted
> tape, and servoed the reel motors to the flux transition rate.
> Obviously the factory had to use a drive with a different tape speed
> control system to format the tape.

DECtape has a timing track, but that can be written on site and simply runs the 
tape takeup motor at its design speed, as far as I can tell.  The reel 
dimensions of DECtape ensure that the speed doesn’t change all that much (min : 
max diameter ratio is rather modest).

paul

Re: using new technology on old machines

[Mark J. Blair]

> On Jun 16, 2015, at 17:52 , Mike Ross  wrote:
> 'remanufacturing' has become part of preservation movements in
> general;
[...]
> Has this ever been seriously considered, or mooted as a possible
> co-operative venture for a group of us?

On this topic, I'm particularly curious about remanufacturing of consumables 
such as magnetic media, printer ribbons, etc. Not only are supplies of unused 
consumables monotonically decreasing, but even remaining ones are succumbing to 
shelf rot (case in point: TU58 cartridges, and particularly their drive belts).

In many cases, it may not be strictly necessary to manufacture the entire item. 
For a TU58 cartridge, the baseplate, case, reels, etc. may be quite usable. The 
tape probably needs to be replaced, but maybe a particular formulation of 
common audio tape could be used instead of manufacturing tape from scratch. The 
belts would certainly need to be manufactured from scratch.

In other cases, even where the item needs to be manufactured from scratch, 
might it be acceptable to use modern methods to manufacture authentic-ish 
replacement consumables? If somebody figured out how to create suitable 
magnetic material and binder for floppy disk media and apply it to mylar 
sheets, for example, maybe a laser cutter could be used to cut out various 
kinds of blanks (5.25", 8", soft-sectored, various hard-sectored 
configurations) without the tooling cost of punching dies that would make more 
sense for mass production?

Would the mentioned automatic wire-wrapping machine need to be recreated in a 
period-correct manner, or would it be acceptable to make one using modern 
expedient hardware in order to use it to create new authentic reproductions?

What sort of concessions could we accept for the lack of authentic components 
to be used? In the case of a locomotive, there are an awful lots of parts that 
could be authentically remanufactured in a regular machine shop (obviously, 
large forgings and the like would be more challenging!). But in the case of a 
computer using particular no-longer-manufactured semiconductor components, the 
thought of bringing up a suitable semiconductor fab to build those components 
would be economically unrealistic.

-- 
Mark J. Blair, NF6X 
http://www.nf6x.net/

Lee Felsenstein says you should read my book :)

[Evan Koblentz]

I am humbled (yes, it is possible!)  got a very nice email from 
Homebrew Computer Club moderator / SOL-20 co-developer / Osborne 1 chief 
engineer (and many more):


"This book presents the history of personal, portable computing from the 
abacus to the present day in a remarkably thorough, accessible fashion. 
Not only the winners are described but the also-rans and 
almost-made-its. Koblentz has done an admirable job of research and 
description in covering the field.


I've always been careful to claim that my Osborne-1 design was only the 
"first commercially-successful portable computer" because I knew that a 
book like this would be forthcoming to show the time lines, descriptions 
and designers of earlier efforts. By nature a survey of the field, it is 
thoroughly researched and can provide pointers to more in-depth 
investigations."


Evan again: still just eight bucks in PDF edition. 
http://www.abacustosmartphone.com.


Also: This is version "1.0"; all first-batch readers will also get the 
PDF of version 1.x for free when it's ready.

RE: using new technology on old machines

[tony duell]

> >
> > Actually, no. That honour goes to the PSU in a Zenith MDA monitor
> > which as I said 'combines the efficiency of a linear with the reliability
> > of a switcher'. The design (if you can call it that) of this PSU is to
> > rectify the mains, feed it into a free-running chopper circuit, then
> > a transformer. The output of that is half-wave (!) rectified giving
> > about 18V DC. Note the chopper free-runs, so there is no regulation
> > applied at this point. That 18V is then fed to a discrete-transistor
> > linear regulator.
> >
> > And that's not the end of the 'curious' design. As you know, a linear
> > regualtor compares the output voltage of the supply with a
> > > reference votlage. That reference voltage is typically produced by
> > a zener diode. Not in this monitor. It uses the drop across the
> > power-on LED. Which means it is important to use a green LED.
> > Another colour, with a different Vf, and the PSU output is wrong.
>

> I would love to have a copy of that schematic for an Engineering Wall of
> Shame. Seriously, that is the strangest supply design I've ever heard.


I don't know if it was ever published [1], but I should have a 
reverse-engineered
version somewhere. When I unpack it (after the move...) I will see about getting
it scanned. It really is a crazy design.

[1] There was the standard 'safety component' warning telling you only to use
the parts specified in the service manual on the back cover. But I was totally 
unable to obtain said service manual.

-tony

RE: Components Data Books

[tony duell]

> Mine too! I just love the old paper books versus PDFs ... and I've got a

So do I. It is a lot easier to filp through a databook than through a collection
of PDFs. 

This has 2 uses : 

1) If you need to find what a house-numbered part really is, you can quickly
look at possible candidates in the databooks to see if any match

2) It was a lot easier to find new components to design with using the paper
books than the PDFs. I can't seem to get the hang of finding interesting new
devices now.

It is convenient to be able to download datasheets sure. But alas this has led
to the demise of the paper databook, you simply can't buy them any more. Oh 
well...

FWIW, I must have over 100 databooks here. Mostly mid 1980s - 1990, but a 
few earlier. 

-tony

RE: using new technology on old machines

[tony duell]

[M452]

> that the original appears to use a 2k 10-turn pot, and a 7440 output buffer,
> neither of which are in my rather extensive junk box.
> In fact the 7440 are rather rare, and I see the cheapest I can get them for
> is around $4.00 each.

True. But you don't need either to build and test the oscillator circuit. The 
7440 is
an output buffer, if you want to build a test version of the entire module you 
could
stick a '20 there or just about any other TTL inverting gate. But I was 
thinking of just
testing the oscillator part which is Q1 and Q2 (again the other 2 transistors 
are buffers)

The preset clearly sets the frequency. You could build the oscillator with say 
a 1k
resistor there at least to put a 'scope on various points to understand how it 
works.


> I am really used to RF circuits so am puzzled there is no inductor. It kind
> of looks like a Darlington Pair but it isn't.

RC oscillators have been around since the 1930s.

> > I will leave the flames about Spice and simulation packages in general for
> > another day.
> 
> You are touchy. Would it help if I used the original Spice2 written in
> Fortran IV. It still works. Sadly I don't have a real mainframe but have to
> use Hercules to run it

OK, I sort-of forgot the smiley, but only sort-of.

The problem is that people try to understand a circuit by throwing it on the
simulator and really don't understand what is going on at all (this assumes
the simulator gets it right which is not always the case). I prefer to think 
about
it. work out how the capacitor (there is only one!) charges and discharges, 
since
that must be the key to the oscillations.

-tony

RE: PDP-12 Restoration at the RICM

[tony duell]

> 
> The PDP-12 came to us with an M452 for the 110 baud TTY console and a
> home-made adjustable baud rate module for the second serial port. The
> adjustable baud rate generator was made by the original user of the system
> in the early 80s, and is just a crystal, rotary switch and a Fairchild
> 4702. I ordered a replacement Intersil IM4702 so we can repair the module.
> The original owner doesn't remember ever having an M405 for the second
> serial port.

Right... (and please stop sending me on wild goose chases)

The 4702 is a well-known baud rate generator IC, basically a crystal oscillator
and divider chain in one package. It generates 16" baud rate outputs as needed
by most common UART chips. As you imply it wasn't really contemporary with
the PDP12, but in this case there is 'provenance'.

I do not believe it is a replacement for just an M405 though. The M405 is a 
simple
crystal oscillator, the output is at the crystal frequency. Now supposing you 
wanted
1200 baud. You need 19200Hz at the (16*) input to the serial circuitry. I've 
never seen
a crystal that slow. There are 32768Hz crystals, of course, and then we jump to 
100kHz
and up. So I woulg guess the original design was to use an M405 and another 
module
(perhaps another M216) as a divider. 

-tony



--
Michael Thompson

OT? Compaq 5/60M

[william degnan]

I know I keep pushing the boundary of vintage lately but I wanted to report
to those who care that I finally got my hands on a 1993 Compaq 5/60M - this
is "a if not the" first desktop computer with a Pentium processor installed
stock.  it was the 1993 "dream machine - $9000+   It had an EISA bus and
was otherwise a 486 system with a Pentium controller card, not on the
motherboard.  Pentium computers' contribution to the WWW era vintage is
extremely significant.

Pentium killed the minicomputer, or at a minimum merged into it, if you ask
me.  The interplay between DEC/Compaq/HP/Intel 1992-1995 culminating into
the launch of Pentium processor systems is vital to understanding the WWW
era of computing.  How these companies worked or did not work together and
how the Pentium vs. the Alpha processor came to be...a good tale of woe and
$$.

For those interested:  Compaq 5/60:
http://vintagecomputer.net/browse_thread.cfm?id=612

I have a bunch of articles to post on my site related to the first Pentium
desktops which I will do asap.

Bill

P.S. while we're on this off-sh topic I also posted some photos of a
Digital 486 laptop, DEC had a 486 laptop before it was absorbed by Compaq.
1994.  Not really noteworthy other than the Digital name
http://vintagecomputer.net/browse_thread.cfm?id=613

P.S.S. and related to Pentium and DEC ... here is one of DEC's early (but
not the first) Pentium machine
http://vintagecomputer.net/browse_thread.cfm?id=585

RE: PDP-12 Restoration at the RICM

[Michael Thompson]

>
> Date: Mon, 15 Jun 2015 19:42:42 -0400
> From: Michael Thompson 
> To: cctech 
>
> The M452 creates a 220 Hz clock for the TTY transmitter and a 880 Hz clock
> for the TTY receiver.
> The M405 for the DP12-B serial port generated a clock that is 16x the baud
> rate which is then divided by an M216 module.
>
> Michael Thompson
>
>
Just to prolong this discussion...

The PDP-12 came to us with an M452 for the 110 baud TTY console and a
home-made adjustable baud rate module for the second serial port. The
adjustable baud rate generator was made by the original user of the system
in the early 80s, and is just a crystal, rotary switch and a Fairchild
4702. I ordered a replacement Intersil IM4702 so we can repair the module.
The original owner doesn't remember ever having an M405 for the second
serial port.

-- 
Michael Thompson

Re: using new technology on old machines

[Pontus Pihlgren]

On Wed, Jun 17, 2015 at 12:52:23PM +1200, Mike Ross wrote:
> 
> Has this ever been seriously considered, or mooted as a possible
> co-operative venture for a group of us?
> 

I see it on the small scale all the time. Such as Rod's new front panels 
for the 8/e. Or the various replica kits for early micros.

One computer I could imagine would sparc interest is a new PDP-6. Not 
sure how that would materialise.

I have a theory as to why it hasn't happened yet though. And that is 
lack of skill. Take an average sized Swedish town and you can probably 
scrounge up a fair amount of welders, carpenters, painters and 
metalworkers willing to work on a fun medium to large scale project such 
as restoring trains, cars and even whole factories. And given the number of 
"industry heritage" museums in Sweden it's a fairly big group.

But finding the a good sized group of people with the right skills for 
wirewrapping a large scale backplane and populating it with period 
correct hardware... much harder I think.

There are other problems too, finding a big chunk of metal to machine a 
new crankshaft is not so hard. Where do you find enough germanium 
transistors for a PDP-6 (I'm guessing that is what was used, and I'm 
also guessing that they are less common today, please correct me if I'm 
wrong)

I would love to work on such a project though!

/P