Resolved: VAX-11/750 ECKAL (Cache/TB) Diagnostic failure
derschjo at gmail.com
Thu Apr 21 22:15:46 CDT 2016
Hey all --
I resolved the weird failure I was seeing on my 11/750 with the Cache/TB
diagnostic and since it was fairly random I thought I'd share it to save
people from the future (hi, people from the future!) from going through
the same machinations I did.
Issue: ECKAL diagnostic loads, prints banner and halts after about a
No other diagnostic is provided, and since there don't appear to be any
listings or real documents covering the test, it's not particularly helpful.
What I tried (prior to tonight):
- Checked voltages.
- Double-checked backplane for bent/shorted pins.
- Cleaned and reseated every socketed chip (especially the gate
arrays). On *all* boards.
- Swapped in a spare L0003 (after cleaning, as above).
- Swapped in all the other spares I have (one at a time, again, after
- Cleaned backplane with contact cleaner.
- Removed 2nd UNIBUS card.
- Tried a *third* L0003 card (labeled "GOOD" as of 1996 :)).
No change in behavior whatsoever. Very odd. Very frustrating.
So tonight I thought, hey, why not disconnect the UNIBUS just in case
something odd is going on there. Pulled the Unibus jumper connecting
the two backplanes, replaced with terminator.
ECKAL diagnostic now runs and passes.
So: This particular fault (at least in this case) is due to some oddity
on the UNIBUS. I suspect a problem with NPG grants, but I'm going to
have to go over this with a fine-toothed comb, it could be a bad
controller in there doing something mean.
Hope this helps someone at some future date...
More information about the cctalk