KDJ11-B PDP 11/73 getting stuck in Exit standalone mode diag #56

Mark G Thomas Mark at Misty.com
Sun Apr 2 13:49:57 CDT 2017


I picked up an empty 4x8 Q-bus chassis at VCF-East this year. It's 
labelled "USDC CSS-823 Processor System" on the outside. It's not a DEC 
backplane, but the chassis is light aluminum, smaller and in some ways 
nicer than my pile of BA23s. It includes a switching power supply, 
LTC and q-bus termination, and I confirmed it's wired for Q22. I was 
hoping to transplant an 11/83 into it, since it will fit more comfortably 
in my work area. It has lit DCON/RUN/LTC/HALT buttons on the front pane.
The etching on the backplane says something like "MDB Systems, Inc.
East Orange, CA 92665"

Unfortunately, I discovered slots are all wired Q22/Q22, no top ABCD 
(Q22/CD) PMI slots like a BA23. So, not good for an 11/83 CPU wired 
for PMI on slots C-D.

So, I was hoping I could get my KDJ11-B (quad-wide 11/73) running in it.
Upon power up or reset I get "Testing in progress. Please wait" on
the serial console, and the LEDs get stuck on test 56. CTRL-C doesn't do 
anything yet, and my only options seem to be to hit reset, or if I hit the 
run/stop toggle, I can reset to the ODT prompt. This is with either just 
the KDJ11-B in the top slot, or with the addition of a suitably configured 
MSV11-QA in the next slot. If I turn off the LTC on the front panel,
I get the expected Error 61 M8190 clock error, PC and register values,
and options to re-run once or loop on test, so I know the LTC is working.

I confirmed the KDJ11-B works fine in a BA23, getting past test 56. I also 
tried an 11/53 CPU here in the ABAB backplane and that gets past the self 
tests into dialog mode, but I really would like to get the KDJ11-B working
in this chassis. I do see that a couple traces to the KDJ11-B C-D slots
besides the Grant Continuity connections. I assume since the KDJ11-B
has those Grant Continuity connections on slots C-D, it can run in a
qbus/qbus Q22/Q22 quad Q-bus slot.

I noticed the FP "RUN" lamp never comes on (and is not burned out), but maybe
that's normal -- monitoring something on the bus that doesn't happen during
power on self test.

Does anyone here have suggestions about next steps in diagnosing this?

4.10.18 Exit Standalone Mode (Test 56) 

In the 22-bit mode, the exit standalone mode is checked by using the 
guaranteed timeout address of 17 760 000 to verify that the timeout 
logic works without hanging up the CPU. 

Mark G. Thomas (Mark at Misty.com), KC3DRE

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