PDP-11/45 RSTS/E boot problem

Jerry Weiss jsw at ieee.org
Wed Feb 13 19:20:14 CST 2019

On 2/13/19 1:43 AM, Fritz Mueller via cctalk wrote:
> Put the M795 out on an extender, loaded 167777 in RKBAR, and had a look around with a logic probe.  Narrowed it down to E34 (a 7430 8-input NAND).  Pulled, socketed, replaced, and off she goes!
> I can now successfully boot and run both V6 Unix and RSTS/E V06C from disk.
> *THAT* was a really fun and rewarding hunt :-)  First message in the thread was back on Dec 30, 2018.  Lots of debugging and failed DRAM repairs, then the final long assault to this single, failed gate...
> Thanks to all here for the help and resources, and particular shout-outs for Noel and Paul who gave generously of their time and attention working through the densest bits, both on and off the list.
> I predict a long happy weekend and a big power bill at the end of the month :-)
>      cheers,
>        --FritzM.
Congratulations.  Well Done.

I am trying to understand how the diagnostics didn't reveal this 
defect.  I see in the source for the diagnostic DZRKH-F there are tests 
for address in the 28K-32K range and also for the 32K boundary.

I'm trying to make sense of the M795 to get a better understanding. Any 
addition data on how the 7430 failed (input bad, output bad, etc ?)


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