Following up on my on post, and top-posting at that :-)
IT WORKS NOW!!!
Apparently, I hadn't actually swapped two of the cards that
I thought I had.
It was the G021 swap at A31/A32 that didn't appear to have
happened. Swapping it again (anyway) moved the problem to
another bit.
I had to pull a G021 out of my PDP-12 to fix the 8/I :-(
Now I can run a small program!!!
0000 2010 ISZ 0010
0001 5000 JMP 0000
0002 7001 INC
0003 5000 JMP 0000
This flashes (almost) all the lights in the accumulator in a nice,
slow, count up. I say almost, because apparently an M220 is still
broken and doesn't carry. I've found it, now just to fix the chip.
OH HAPPY DAY! :-)
Cheers,
-RK
Robert Krten sez...
>
> O. Sharp sez...
> >
> > I finally got the original post, along with the followup. :)
>
> :-)
>
> > It suddenly dawned on me that I've got the memory-extension schematics
> > on my hard drive (thank you, Mr. Kossow!), and can actually look at
> > them without digging through the storage room...
>
> Yes, Al's site is an *excellent* resource!
>
> > In the Memory Extension Control the MB is indeed buffered, and becomes
> > the MCBMB (presumably "Memory-Control-Buffered Memory Buffer").
> > Curiously, it rebuffers the MB by taking the signal from the _other_
> > side of the original MB00 flip-flop - e.g., MB00(1) - and inverting
> > it prior to use. I'm guessing this is to minimize rewiring of the
> > backplane when installing the extended-memory option. The inversion
> > for MB00 takes place on the M617 at B12. Does the problem move down to
> > MB06 if you swap the M617s at B12 and B13? Similarly, is the MB00(1)
>
> Swapped; no change :-(
>
> > signal making it from E34 pin T2 to B12 pin A1?
>
> Yup. Connection exists on the backplane...
>
> > I don't know if that'll make a difference, but I'm hoping. :) The
> > rebuffering looks like it's primarily for extensions located off the
> > main board, but it may affect the first two 4K stacks as well.. I'm
> > not sure what wiring changes, if any, are done on the 8/I backplane to
> > accomodate the memory-extension control, or whether the MB/MCBMB
> > signals are a part of that. Anyone know of a reference for this?
> >
> > Anyway, that's my thought. I hope it helps, because if that isn't it
> > the guesses start getting esoteric. :) :)
>
> Bring on the esoteric guesses! :-)
>
> Thanks,
> -RK
>
> --
> Robert Krten, PARSE Software Devices +1 613 599 8316.
> Realtime Systems Architecture, Consulting and Training at www.parse.com
> Looking for Digital Equipment Corp. PDP-1 through PDP-15 minicomputers!
>
--
Robert Krten, PARSE Software Devices +1 613 599 8316.
Realtime Systems Architecture, Consulting and Training at www.parse.com
Looking for Digital Equipment Corp. PDP-1 through PDP-15 minicomputers!
Received on Wed Nov 05 2003 - 17:08:15 GMT