Resolved: VAX-11/750 ECKAL (Cache/TB) Diagnostic failure

Josh Dersch derschjo at
Thu Apr 21 22:42:29 CDT 2016

And to reply to my own mail:  The issue was an improperly installed TU80 
controller (it wasn't me!).  The NPG jumper was not removed from the 
backplane when the card was installed.

So:  Double-check your grants, even when testing something seemingly 
unrelated, like your cache.  Lesson learned.

- Josh

On 4/21/16 8:15 PM, Josh Dersch wrote:
> 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 
> second with:
> 00003488   06
> 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 
> cleaning).
> - 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...
> - Josh

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