memtest86 reboots

I have two new Athlon 64-based computers.  I'm having an odd problem with
KNOPPIX on both.

To test the memory, I tried to run memtest from the KNOPPIX 3.4 CD's
boot: prompt.  As soon as it starts to run memtest, the system reboots.
I wonder what is wrong?

I have no trouble running memtest from the KNOPPIX boot prompt on
another machine (happens to be an IBM a20p notebook).  It therefore
seems unlikely that the CD is bad.

This happens on both Athlon 64 machines (they are pretty similar HP
machines).  So the problem must be generic to this model rather than
being a problem with a specific machine.

I get the same behaviour with the memtest on the Fedora Core 1 CD.  So
it isn't a problem unique to KNOPPIX.

KNOPPIX itself will run just fine on these machines.  So they must be
mostly working.

memtest works when it is run from a memtest boot floppy (only one of
the Athlon 64 machines has a floppy drive).  So the problem is not in
memtest itself.

What could be going wrong?  Is there anything tricky about the
transition to memtest86 from the KNOPPIX (or Fedora) boot: prompt?

The BIOS on these Athlon 64 machines is not the latest.  I cannot
update it because HP only provides a way of flashing from Windows XP.
I don't have Windows XP.

I would welcocme ideas about how to attach this problem.

Thanks,

Hugh Redelmeier
[email protected]  voice: +1 416 482-8253