On Sat, 20 Jul 2002, Hugh Graham wrote:

> Saying all that makes finding DEC's programmer sound a whole lot safer.
> Maybe one of the DECUS derivatives can scare up the necessary resources
> if asked nicely.

  I have asked our DEC/Compaq/HP service person if he could find out
anything through his channels.

> Hmm, since you have more information on how this chip may work, maybe
> you can try some new combinations of the dz misprobe. When I had Chuck
> Cranor boot my attempts at setting things right, I never had the 0x40
> write setup in there. Perhaps this part can restore some bits without
> requiring a full erase first after all.

  Unfortunately, the AMD chip doesn't work that way.  You have to erase
the chip to all ones, and then clear the bits to program it.  Once a bit
is cleared, it can only be set by erasing the entire memory.

> If not, tracking down the firmware's checksum routine may be useful,
> in case it has a special case for an all-zeros checksum, or can be
> zapped to always return success.

  I've tried a simple 32 bit sum, and didn't get any useful result.
Somewhere in all the code in those images should be the test it uses to
verify the PROM.  I've disassembled it with objdump and scanned it very
briefly, but didn't spot anything.  The objdump output is 145,000 lines,
which is a lot to grovel through, and objdump probably messes up some of
the disassembly.

--
Michael L. Hitch			mhitch@montana.edu
Computer Consultant
Information Technology Center
Montana State University	Bozeman, MT	USA