On Thu, 2023-02-02 at 17:44 -0800, Sellam Abraham via cctalk wrote:
> On Thu, Feb 2, 2023 at 3:45 PM Van Snyder via cctalk <
> cctalk@classiccmp.org>wrote:
> > On Thu, 2023-02-02 at 18:28 -0500, William Sudbrink via cctalk
> > wrote:
> > > After more than three years, U of Iowa's PDP-8 project acti
On Thu, 2 Feb 2023 at 11:54, emanuel stiebler via cctalk
wrote:
>
> On 2023-02-02 04:38, David Brownlee wrote:
>
> > That reminds me (looks at 43.5T of zfs pool that has not had a scrub
> > since 2021).
> >
> > It can be nice to have a filesystem which handles redundancy and also
> > the opti
> On Feb 3, 2023, at 1:12 AM, Chuck Guzis via cctalk
> wrote:
>
> On 2/2/23 21:23, Tom Hunter via cctalk wrote:
>> The actual ferrite core doughnuts do not break down with continued use, BUT
>> moisture or mechanical impact or vibration will damage or degrade the
>> ferrite cores. Otherwise t
> On 02/03/2023 8:25 AM CST Paul Koning via cctalk
> wrote:
> It's puzzling that temperature would matter. Obviously, when you hit the
> Curie temperature the data goes away, but for typical magnetic materials that
> is in the hundreds of degrees. Does the hysteresis curve shift enough at
On Fri, Feb 3, 2023 at 2:41 PM Will Cooke via cctalk
wrote:
> Yes. The thresholds shift with temperature. Some companines (DEC?) used
> temperature-compensated amplifiers to address the issue. IBM, on some models
> like the 1620, kept the cores at a constant (elevated) temperature.
Most of
On 2/3/23 08:25, Paul Koning via cctalk wrote:
It's puzzling that temperature would matter. Obviously, when you hit the Curie
temperature the data goes away, but for typical magnetic materials that is in
the hundreds of degrees. Does the hysteresis curve shift enough at moderate
temperature
Question: I just used a strong magnet to wipe an old Maxtor MFM drive
(magnet on outside of case). Now the drive will not even seek properly
on start up, just endlessly moves the heads..
Is the drive now toast? Do MFM drives have embedded servo information on
the platter formatted by the facto
low level format
On Fri, Feb 3, 2023 at 11:40 AM Chris Zach via cctalk
wrote:
> Question: I just used a strong magnet to wipe an old Maxtor MFM drive
> (magnet on outside of case). Now the drive will not even seek properly
> on start up, just endlessly moves the heads..
>
> Is the drive now toas
On Fri, Feb 3, 2023 at 4:40 PM Chris Zach via cctalk
wrote:
>
> Question: I just used a strong magnet to wipe an old Maxtor MFM drive
> (magnet on outside of case). Now the drive will not even seek properly
> on start up, just endlessly moves the heads..
>
> Is the drive now toast? Do MFM drives h
On 2/2/23 23:07, Tom Hunter via cctalk wrote:
> Chuck, the CDC 7600 duty cycle integrator is really a work-around against
> overheating and has nothing to do with core reliability and/or endurance.
>
> Core and the data stored in it lives "forever" if the operating constraints
> of the medium are
On Fri, Feb 3, 2023 at 4:45 PM Chuck Guzis via cctalk
wrote:
>
> Another problem with very old core is that its physical integrity is
> often an issue. Cores can crack, being essentially ceramics. I'm
> reminded of the CE fishing around in the oil bath of a 7090 with what
> amounted to a magne
Embedded servo is rare (unheard-of) on ST412 interfaced drives simply
because the manufacturer has no idea how it will be low-level
formatted and thus where the sector headers will be. So no safe place
for the servo bursts on the data surfaces
*nod* That's what I would think: MFM should allow yo
Decided to spend some time working on my 11/73 with MFM drives.
Currently it has one of my RQDX3 boards (I have 3, 1 in attic), a 40mb
ST412 drive (the half height Seagate whatever) which works fine. No
issues there.
I'm trying to format an RD54 compatible drive and am running into major
issu
On Fri, Feb 3, 2023 at 4:57 PM Chris Zach via cctalk
wrote:
> Yep, with 15 yeads it had a servo platter that is gone. Oh well, it's
> securely erased :-) I'll toss the drive, keep the electronics interface
> and keep it in mind for the future.
If you have the tools, it's worth carefully dismantl
On 2023-02-03 12:09, Chris Zach via cctalk wrote:
Decided to spend some time working on my 11/73 with MFM drives.
Currently it has one of my RQDX3 boards (I have 3, 1 in attic), a 40mb
ST412 drive (the half height Seagate whatever) which works fine. No
issues there.
I'm trying to format an RD
I thoug the right one was st512...can you enlighten me on this subject Tony?
Enviado do meu Tele-Movel
> I assume by 'MFM' you mean a drive with an interface similar to the ST412.
> -tony
>
Or ST506 ?
On Fri, Feb 3, 2023 at 5:21 PM Alexandre Souza via cctalk <
cctalk@classiccmp.org> wrote:
> I thoug the right one was st512...can you enlighten me on this subject
> Tony?
>
> Enviado do meu Tele-Movel
>
>
> > I assume by 'MFM' you mean a drive with an interface similar to the
> ST412.
On Fri, Feb 3, 2023 at 5:21 PM Alexandre Souza
wrote:
>
> I thoug the right one was st512...can you enlighten me on this subject Tony?
I've never heard it called that.
It's often called 'ST506' but that drive had a few differences from
the later ones. it didn't support buffered seeks AFAIK. The
On Fri, Feb 03, 2023 at 12:09:27PM -0500, Chris Zach wrote:
>
> Question: Can Dave G's board be used to low level format an RD54? Can it
> test physical disk for errors (wasn't sure)
>
The read test you did should have told you if there were sectors with errors.
Using my tools to low level forma
On 2023-02-02 4:44 p.m., Van Snyder via cctalk wrote:
On Thu, 2023-02-02 at 18:28 -0500, William Sudbrink via cctalk wrote:
After more than three years, U of Iowa's PDP-8 project active again
Years ago, I had a colleague named Prentiss Knowlton who built a
solenoid bank to connect to his PDP-8
I do have an RD54 image that can be used with mfm_write. Search in page for RD54
http://www.pdp8online.com/mfm/status.shtml
Ok. Hm. So the command would be ./mfm_write --emulation RD54_A -d3?
This is possibly better than nothing: I could use this to put some sort
of format on the drive, then t
The ST512 was a thin-film head version of the ST506, per Seagate :
"This increased capacity is accomplished by using the inner portion of the disc
surface that was previously unused and by increasing the disc track density
from 255 tracks per inch to 270 tracks per inch To reliably use the inner
On 2/3/23 10:22, ben via cctalk wrote:
> Could be hiding in the Organ. :)
> They don't make I/O devices like that any more.
> Ben.
Very old technology. Pre-electronic Welke Vorsetzer, electronics
Marantz Pianocorder and the full-integrated into pianos Sony Disklavier.
Remember the radio program
Wow, this is interesting Dave. Took one of the "formatted badly" disks
and did a write of your file.
root@beaglebone:~/mfm# ./mfm_write --emulation RD54_A -d3 -c1224 -h15 -s 17
Board revision C detected
Then a read of the disk:
root@beaglebone:~/mfm# ./mfm_read --analyze -e rd.dsk
Board revis
I have the following Q-BUS boards available.
M7168 VCB02, QDSS Q 4-plane colour bitmap module
M7169 VCB02, QDSS Q 4-plane video controller module
M7608 MS630 RAM for KA630
M7608 MS630 RAM for KA630
M7606 KA630 Microvax II CPU
M7620 KA650 Q MicroVAX III CPU
M7165 Qbus SDI disk adapter
I also
On 2023-02-03 16:47, David Coolbear via cctalk wrote:
I have the following Q-BUS boards available.
M7168 VCB02, QDSS Q 4-plane colour bitmap module
M7169 VCB02, QDSS Q 4-plane video controller module
M7608 MS630 RAM for KA630
M7608 MS630 RAM for KA630
M7606 KA630 Microvax II CPU
M7620 KA650
Chris, what kind of magnet did you use?
If it was an electromagnet I could imagine that you caused physical damage
by something heating up sufficiently. If it was a permanent magnet then it
might indeed be servo data which has been erased. Either way I expect you
need a very strong magnetic field t
Well, formatting an RD53 seems to be working. And the rev 4 ROMs are
much nicer than the rev 3 in terms of talking to you.
Unit Cylinders Drive Name
0 1024 RD53
1 RX33 Diskette (FORMATABLE)
MSCP Controller Model: 19
Microcode Version: 4
Formatting of Drive 0
Some thoughts on this day of working on MFM drives:
1) MFM drives are just going bad. They were always kind of meh in terms
of reliability, but I think even since 2019 (the last time I checked
these drives) things have gotten worse. Drives which were readable and
good then are now either shot
I’d just like to say that 25 years ago, RD53’s were *EVIL*. I do have one that
I should try taking apart. I failed to back it up the first time I powered it
on. It didn’t boot the second time.
ESDI or SCSI is the way to go, at least that was true 20-25 years ago. Today
I’d be inclined to sa
Yeah at this point pop it open, unlock the heads (the white cam down at
the base there, trip it) and get the heads to move. They should smoothly
move with a bit of effort. Then fire it up and see if anything works.
I'm going to run this one for a bit in the backup pdp11 here, see if it
runs if
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