AT&T PC 6300 Plus Unix box

From: Bill Yakowenko <yakowenk_at_cs.unc.edu>
Date: Wed Sep 29 16:15:55 1999

Hey all,

Yesterday I scooped an AT&T PC 6300 Unix machine on its way
to the dumpster. Got it home, powered it up, and now I know
why. It displays "Parity error on system board" and locks
up. Actually, it displayed a bit more:

        Resident Diagnostics
        Ver 2.05P
        
        CPU (i286) PASS
        ROM Module PASS
        DMA Timer PASS
        DMA Control PASS
        Interrupts PASS
        Parity error on system board

It seems to have 1MB of RAM, half socketed (36 81256's).
So I yanked the socketed chips, and tried again. Then
it did almost the same thing, but displayed a running
count up to 512K before that parity message.

So, what's next? I'm guessing that at least one of the
socketed chips was bad, because it got farther before
barfing when they were removed. But there is some other
problem too, maybe in the soldered-in RAM chips, or
maybe in the parity-check circuit itself.

Anybody got a service manual or schematics or a big pile
of clues for this thing?

        Cheers,
        Bill.
Received on Wed Sep 29 1999 - 16:15:55 BST