PDP-11/23 Debugging

Ben Sinclair bensinc at gmail.com
Tue Nov 18 15:18:05 CST 2014

On Tue, Nov 18, 2014 at 2:22 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu>

>     > From: John Wallace
>     > Perhaps not so obviously,11/23 boards were available in variants with
>     > or without floating point, and (iirc) with or without memory
> management
>     > unit (MMU) (correction welcome).
> No, you're right on target. (Although one couldn't have FP without the MMU;
> the FP registers were actually in the MMU chip, see MicroComputers+Memories
> '82 pp. 350-351.
>     > is it vaguely conceivable that the diagnostic in question needs a
> piece
>     > of hardware that isn't on the board in question
> Hmm. Possible, but from what I know, unlikely. That test claims to test:
> Part 1 - the CPU checks out the basic PDP11 instructions in every
> addressing
>   mode with various data patterns.
> Part 2 - tests all trap instructions, trap overflow conditions R6,
>   interrupts, the reset and wait instruction.
> Part 3 - tests the EXTENDED INSTRUCTION SET, the ASH, ASHC, MUL and DIV
>   instruction
> all of which are, AFAIK, part of the basic chip. (Unlike the 11/03 and
> 11/40, where MUL et al are part of the optional EIS.)
> Although I see 'interrupts' listed there - I wonder what they are using
> to generate the interrupt? The console serial line? Must be, I can't think
> of any other device in the config he was testing.
> Ben, you didn't have a discontinuity in the grant jumpering, did you?
> What kind of backplane do you have, and in what order/slots were the
> boards plugged in?
>     > or is seriously broken on the board in question?
> That is the other possibiliy.
> Ben, do you get the same error with both CPU cards? Do you have spare
> memory/serial line cards you can swap in?
>         Noel

I don't believe I have any discontinuity, but how would I tell? I think
with my backplane (H9273) I'm supposed to put everything down the left
side, with the BVD11 at the bottom.

Currently I have starting from the top left and going down the left side:
M8186, M8044, M8043, then the BVD at the very bottom.

The only other CPU card I have is the one with that mod and no jumpers. I
did swap the CPU And MMU chips, and they both seem to do the same thing.
I'll add jumpers to the other CPU board and try it out as well!

I have another memory board, but I know it's bad, so I can't try that!


Ben Sinclair
ben at bensinclair.com

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