Now the TK50 problem

Now the TK50 problem

[Michael Sokolov]

Hi,

Having solved the RA72 problem and the KDA50 problem, I'm ready to attack the
next problem. :-( This time the TK50. I have a very odd problem with it. When I
first power up the VAX, everything works fine. I can read tapes, restore dumps,
etc. Then after some uptime (apparently something heat-related) it starts
behaving very oddly. Tapes with 512-byte records still read just fine, but
trying to read a tape with 10240-byte records (such as a UNIX filesystem dump
tape) results in the controller returning a hard error indication of "record
data truncated". This is so odd that I first thought it was a software problem,
but it isn't, because this happens identically under 4.3BSD-Quasijarus0 and
Ultrix V4.0, whose TMSCP drivers are completely different. The fact that the
problem occurs only after some uptime suggests some kind of overheat, which
would normally be a very low-level physical problem, but the record size
dependence suggests something high-level, more likely the controller than the
drive. This MicroVAX is still under the dealer's warranty (I just bought it on
Monday), so if this is a bad drive or controller, I can replace it, which which
of the two is it? Has anyone ever seen this problem before? Does anyone know
whether it is the drive or the controller that's bad? TIA.

--
Michael Sokolov
Special Agent
International Free Computing Task Force

ARPA Internet SMTP mail: msokolov at meson.jpsystems.com

P.S. The temperature in the machine room is 70F. Not the best for a machine
room, but the best you'd ever expect for an office, and I think the VAX has no
right to go on strike at 70F.