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. Best, J