VAX 750 tbuf machine checks

[Roy Smith]

> Our final solution to the problem [...] was to get a DEC certified board
> that was tested and run on UNIX 4.2BSD.

	After 18 months of almost flawless operation, our 11/750 has
developed the dreaded "cp tbuf parity error" disease.  I've been going
around in circles with field service for 3 weeks now with no success (can
you say "let's swap the L0003 board again"?)

	DEC even went so far as to suggest that not having my uda-50 at the
end of the Unibus was to blame, and we spend a half a day pulling it out of
the system box and moving it to the expansion box.  Note, as a peripheral
matter, that the uda-50 came factory installed in the wrong slot, and all
this bus shuffling was done after we got a hard failure running ECKAL with
the entire Unibus disconnected!  Naturally, now we've started to develop
the dreaded "SDI error; event 053" disease" as well.

	Anyway, according to the field disservice branch manager here in
NY, DEC is no longer Unix-testing boards!  From what I can make out, the
group that was doing the Unix-testing doesn't exist any more.  Our F.S.
branch manager is looking into getting them to start up again and do
another batch of boards, but it doesn't look like that's going to happen.

	There seems to be Yet Another redesign of the L0003 module in the
works (the L0003-YA, I think) which will cure the problem, or so they say.
It looks like we're going to be a test site for the new board, so stay
tuned for further details.  Rumor has it that they are working on a rev 8,
which will *not* require people to load any new micro-code.  I don't know
if this new L0003 and rev 8 are the same thing, but I think they might be.

	If this article seem to be liberally sprinkled with phrases like
"seems to be", "looks like", "according to rumor", etc., there is a reason.
All of this is true to the best of my knowledge, but that knowledge is not
guaranteed to be very good.  Corrections and/or clarifications from more
knowledgeable people inside of DEC would be most appreciated.
-- 
Roy Smith <allegra!phri!roy>
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016