Hello to Everyone that replied to my post on the HP7970 Tape Drive.
I very much appreciate the advice and counsel.
Sorry for the delay responding, I had a medical procedure that
knocked me back a bit - nothing serious, just mostly irritating (the
ENT Doc injected 25ml of a liquid steroid direct into my inner ear
Cochlear through penetration of the eardrum - Yuck!) <Whining>
My goal is to understand the feasibility of connecting a 7970 to the
68K system that I have assembled.
I do not yet have a 7970 and it is probably a bit of a wait to find one.
I begin to believe that such a project is feasible, especially
considering that people have done that sort of thing before to other
processors.
Best that I can tell, there are no device drivers whatsoever for the
Motorola 68K - Please let me know if I am wrong.
I begin to believe that a possible path would be to use a VMEbus
digital in/out board to connect possibly direct to the HP7970
control/read/write lines and then build ASM software to control that.
Running on a 50Mhz 68060 processor gives me hope that I will be able
to stay ahead of the drive. Polling loops running hard should help there.
The key, I think, to that will be finding really detailed timing etc
specifications.
Jay, I will look for documentation on the HP 13181/13183 tape
controller - that certainly makes sense and will give me something to
stare at :)
I just found it at HP Computer Museum: It's a pretty thing:
http://www.hpmuseum.net/images/7970MagTape1-13181-60040-42.jpg
Just downloaded and printed the 13181/13183 tape controller
documentation. I am much stronger in software than hardware, but will
see if I can make sense of it. Mostly what I need are the control
lines: commands, timing...
Regards to the List,
Jack
ps - If interested, see https://www.youtube.com/watch?v=GfT96j-7Zjc
to see what we did with some 68000 boards running ASM/Lisp back in
the day 1985. It was a fun project - I ran and hid in my hole when
that thing was running around - not kidding :)
At 07:58 PM 10/3/2017, Jay West wrote:
Jack wrote...
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I begin to understand - so, for example an HP2100 with the 7970 tape option
had a specific tape controller board that talked direct to the 7970.
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Yep, and no small amount of logic. The 7970A or B interfaced to a 2100/21MX
host using a 13181 interface (which is a two board set). The 7970E
interfaced to a 2100/21mx host using a 13183 interface (which is also a two
board set). Wasn't there some deal where a M/E/F could drive it at 45ips but
a 2100 couldn't (next lower speed)?? I don't recall for sure, but there was
something vaguely like that. And off that 13181/3 board you could have four
tape drives I believe.
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I never used an HP2100 with a "real" tape drive such as the 7970 - actually
just paper tape back in 1974-1978 where I wrote in ASM (a bit ugly with no
index register) and ALGOL (I still have the box of paper tapes somewhere
with that four pass ALGOL compiler - that nice black oiled paper with the
smell :)
--------
No... you did use a HP2100 with a REAL tape drive... such as the 2748B
*grin*Paper tape rocks. I have that same ALGOL compiler I'm sure secreted
away in a paper tape box(es).
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I am delighted to hear that people have actually built a 7970 interface and
got it to work mostly in pure software.
That is good news and gives me hope :)
Interesting indeed.
Jay, I appreciate the helpful response. Thank you.
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Glad to help, but I just copied Chucks post from a few weeks back. He
supplied the knowledge :)
------
I will read the 7970 interface specifications more carefully now that I
understand better the context. The timing issues are, of course, key.
------
HP manuals of the period are awfully detailed. They all have the theory of
operation section with a circuit walkthrough, etc. It could be helpful for
you to also take a look at the manual for the 13181 or 13183 controller set,
as you'll kinda be doing what that boardset does.
Best,
J
----------------------------------------------------------------------------------
Jack Harper, President
Secure Outcomes Inc
2942 Evergreen Parkway, Suite 300
Evergreen, Colorado 80439 USA
303.670.8375
303.670.3750 (fax)
http://www.secureoutcomes.net for Product Info.
