[Simh] VAX 8200

[Gary Lee Phillips]

On Fri, Mar 17, 2017 at 11:05 AM, Paul Koning <paulkoning at comcast.net>
wrote:

>
> 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.
>
>
Our IBM stuff was (IIRC) 3084 by that time, or if not, a dual 370 set up. I
don't remember ever trying to do data interchange on tape with the IBM
systems using that particular drive. When that need came up later on we
deliberately avoided DEC hardware for the second tape drive and got a stand
alone drive unit that was vertically mounted with vacuum columns. I don't
remember the maker's name, but it worked as expected, never required a
service call, and read or wrote any brand of media we used.

In any case, the issue I had was that the particular drive on the 8200
would not read back tapes written even by itself. We used it only for
backups from the hard drive. DEC support was called in several times to
adjust, calibrate, test, etc. It worked best only with DEC-branded media
and if the heads were cleaned before every single use, and finally they
just shrugged and said "Use only our media." Of course, theirs cost about
twice what we paid for the large bulk quantities of 9 track tape used in
the IBM center on the floor below. It wasn't my problem at that point, and
my boss just ordered some tapes from DEC.

--Gary
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