In message , John
Rumm writes
On 14/01/2014 19:24, Ian Jackson wrote:

So the only two conclusions I can come to are "Yes, 'too fast' memory
MIGHT screw up your computer" - or maybe it's simply that I've got a
duff pair of PC-6400 (although they did work OK for a week). As I had
problems with my second pair of PC-6400, maybe they are also duff. If
MemTest doesn't show any problems, I'll next try Mike Tomlinson's test
suggestions.

I think someone has already mentioned Prime95 - but its torture test
will often reveal problems hiding in otherwise apparently working
hardware.

Indeed they did (if it passes Memtest86).

The present situation is that after appearing to run fine, on boot-up
the BIOS stopped detecting one or more drives. Googling for advice on
this syndrome, the many answers are reveal that it could be almost
anything (including there not being an R in the month).

Just in case, I took out the BIOS battery to check it, and it was over
3V (but I'll pop a new one in, just in case). I obviously had it out too
long, as afterwards, the save BIOS settings had reverted (presumably)
the defaults. All drives now seem to be being detected (so far). Just
for luck, I did a 'Load optimised settings" (or whatever it's called),
and it's still OK.

Other obvious problems could be intermittent dodgy PSU connections - or
even a flaky PSU (which I'll be checking).
--
Ian