(Classic Computers) HP 7970 1/2" 9-Track Reel-to-Reel Tape Drive

Jay West jwest at classiccmp.org
Tue Oct 3 20:58:43 CDT 2017

Jack wrote...
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.
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.

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).

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.
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.



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