unbootable 3b1 fixed (summary)

[Augustine Cano]

Hello everyone, and many thanks to those who answered my original posting!

As the header says, my 3b1 is running again.  The culprit: the Data DMA chip.
At least a couple of people said that a DMA chip problem was a possibility.
Recapping the problem, so that this might help someone with similar symptoms:
The machine died with a panic: addr fault in kernel message.  It would not
boot off the HD or the floppy (bootable floppy unix or diagnostics disk), the
loader message never appeared.  It looked like the boot program was alternating
between the floppy and the HD, never getting anywhere.  Each time an access was
made, a new little square on the screen appeared and that was it.
Some people confirmed my suspicion that given that neither drive worked, this
was probably not (as it wasn't) a controller chip problem.

By the way this did not fix the intermittent problem I was having of hard
disk timeout errors (with crash); they still happen.

Of course, before I swapped the chip, I checked that the drives were rotating,
I resocketed the socketed chips, tested power supply voltages and made sure
that all cables were properly plugged.  All these things were suggested by
many people.

The only problem remaining is that I am running now with a BORROWED CHIP that
I have to return.  I need to buy tha DATA DMA CHIP, the one at location 22H on
the mother-board.  Any information on a source would be most welcome.

FLAME ON

Obviously the first place I called when the crash occurred was AT&T.  I talked
to the tech that had changed the HD while the machine was still under warranty.
According to him, the procedure was simple: $45 just to diagnose the problem,
if it was a socketed chip, replace the chip in question, otherwise swap the
board (at $300.00 a shot).  I tried other ways to get it fixed and eventually
found the chip I borrowed.  When I called the tech again to buy it, I got all
kinds of vague answers and runaround.  According to his own procedure of a few
weeks earlier, if the diagnosis was a socketed chip, how was he to replace if
he can't get it?  I called the regular hotline and the parts hotline, where
after being transfered half a dozen times, someone seemed to take some time
to figure out what chip I needed.  He couldn't find it in any of his catalogs.
The conclusion: it's not available.  At his suggestion, I contacted Convergent.
The result: Convergent does not sell retail in any case, plus the machine is
discontinued, so... tough luck.  This person recommended I get in touch with
hardware types on the net.  In any case, the impression I get from AT&T is that
"if you pay us mega-bucks, we'll fix it, if you want to fix it yourself, we
won't help you in any way".

FLAME OFF

Any pointers to locate such a chip will be greatly appreaciated.  Someone at
AT&T that knows about it, the actual chip maker, whatever.

Again, many thanks to those who sent me their invaluable advice.

Augustine Cano		canoaf at dept.csci.unt.edu