Debugging ONMIBUS cards

From: Ethan Dicks <>
Date: Tue Nov 23 21:47:55 1999

OK... take two on this...

I've been working with a pile of hex and quad ONMIBUS cards and a PDP-8/e
and PDP-8/a chassis. At one point I had a working machine, but since last
weekend, something new has flaked out.

I have one KK8E board set that passes basic front panel ops, runs an
inchworm program but does not seem to be able to communicate out the
serial port (M8560). I have a KK8A/DKC8AA/KM8A set that appears to
boot floppies, but gives me funny results on the console. The KK8E
processor board set does not seem to want to work in the -8/a box. The
KK8A does not seem to work in the PDP-8/e box (the Load Address switch
increments the MA register; it doesn't load it).

The best I'm getting out of the -8/a right now is to waggle the floppies
a bit, sort of boot, and drop me at an OS/8 dot prompt. This is even true
of the ADVENTURE floppy that was booting last week. When I type commands
at the prompt, none run, but I get odd error messages. One pattern is that
if I type the command "ADVENT" at the prompt on the advent disk, I get back
"ADFEND" - the letters drop a bit. If I attempt to run a command "UUUU", I
get back "EEEE" as an error. Given that if the CPU or memory or RX8E were
bad the system wouldn't boot, it suggests to me that there is a problem
with the DKC8AA.

My biggest problem is that I have schematics, but without a front panel on
the PDP-8/a, I can't generate discreet operations to run the CPU through its
paces and I can't toggle in simple programs. I have the prints for the
DKC8AA. Is it feasible to build my own front panel? I don't even have one
to copy; I'd be guessing the whole way. If I could use the KK8A in the -8/e
box, I would use _its_ front panel, but that doesn't seem to work either.

Does anyone have any helpful advice to get me past this chicken and the egg
problem? I have prints; I have extender cards; I have a scope. I even have
a logic analyzer, but it's not presently at the same place as the -8's. What
I don't have is a combination of PDP-8 hardware that lends itself to
reasonable testing.

As for the PDP-8/e, does anyone have a simple TTY test routine? I could
write one, but I'd love to see one that has stood the test of time. As I
mentioned above, the inchworm runs fine. I'm presently using all quad cards
except for an MS8-C 32K MOS memory card; I have core, but I don't know where
the box of overhead connectors got left - I only know where three connectors
are and the CPU needs two. I do happen to have a couple of Heathkit backplane
connectors I can wire together, but I'm still short enough to do a proper job.
For now, the MOS memory seems to work fine; it's the M865 and M8650 that I'm
looking into.

Thanks in advance,


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Received on Tue Nov 23 1999 - 21:47:55 GMT

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