[Simh] VAX 8200

[Paul Koning]

> On Mar 17, 2017, at 11:54 AM, Gary Lee Phillips <tivo.overo at gmail.com> wrote:
> 
> ...
> The tape drive was not TK50. It was standard reel to reel media, horizontal like an studio audio tape deck, with a cover that had to be lifted in order to use it. The disk drive was housed in the same cabinet in a drawer below the tape unit. The tape drive was "finicky" and seemed to work only with tapes ordered through DEC. The standard tapes our much larger IBM shop used never read back correctly when written on it.

That sounds like a TU80, TU81, TA80, or TA81, all basically the same transport with variations in density and controller interconnect.  Interesting about the "finicky" thing, I don't have any personal experience with feeding it tapes from other companies.

FWIW, I just saw a comment that some IBM systems (early 360, perhaps) had a habit of inserting short gaps into the middle of tape records because of memory latency issues.  Apparently IBM's drives could read such stuff but other people's drives would not, fair enough since such tapes are not standards-compliant.

More in general, if drive B wont' read tapes written by drive A, the fault could be at either end (or both).  It could even be in the standard -- all too many standards, for example a whole lot of modern network protocol standards, permit implementations that conform but don't interoperate.  In some cases, the authors get annoyed when you point this out and call it a standards bug.  (By contrast, the DECnet standards were always written to the rule that "conformance implies interoperability".)

	paul