PDP-11/45 RSTS/E boot problem

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Feb 4 13:24:19 CST 2019

    > From: Jay Jaeger

    > This sort of situation, where DEC diagnostics run OK but UNIX has issues
    > was reported to be not all that uncommon - to the point where the urban
    > legend was that some DEC FE's would fire up Unix V6 as a sort of system
    > exerciser.

Amusing! Never heard that; our -11's were never under maintenance, so DEC FE's
never worked on them.

    > Make a copy of ls, and see if the copy also fails

It acts just like the original; fails when run by itself, runs OK when 'sleep'
is also running (in the background).

    > From: Bob Smith

    > We finally had the cpu backplane replaced

Ow. Not an option for Fritz, I expect. (I dunno - anyone have a spare /45

    > From: Paul Koning

    > Is there any way to attach a logic analyzer to various data paths on
    > this machine?

I had suggested to Fritz that the symptoms led me to believe that it was time
to deploy a LA, especially since the MM trap only occurs once between him
typing 'ls' and the process failing - i.e. easy to trigger on.

He offered me the options of look at the IR or at the UNIBUS - I opted for
the IR so we can see _exactly_ what the machine _thinks_ it is doing! No
report back yet, though.


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