[Gllug] BIOS setting of clock speed

[Kristian Davies]

|I have had a couple of instances of PCs playing up (running Windoze as it
|happens !); in once case Windows would not install on a new PC and in the
|other case the PC which had been running fine for ages suddenly starting
|misbehaving.

|In both cases the problem turned out to be the BIOS setting the processor
|speed too slow. In the first case, on install on a new machine, the BIOS
|actually warned that the higher (correct !) speed might cuase unstable
operation
|or somesuch; so the defaulted lower speed was initially accepted.  Changing
|to the higher speed solved the problem.  In the second case it appears that
the
|the clock speed somehow flipped down on its own accord.  Resetting it to
the
|higher speed solved the problem.

We have some old AMD machines with Asus motherboards.  When they crash they
reset the CPU speed to a default low setting.  This will probably also
happen if you set the clock setting too high, in which case when you reboot
it will be at the same default low setting.  This stops you having to short
the battery or something to reset the bios (I think).

|I ran memtest86 on the second occasion before and after changing the clock
speed
|back up.  A number of errors were noted at the lower speed, but none at the
|higher speed.

|I can only assume that at the lower speed (with, as I recall, a
correspondingly
|power FSB speed) the memory cells are refreshed at a slower rate and
|occasionally some of them 'lose' their contents.  Of course, it maybe due
to
|something entirely different !  However,  it does appear that
'underclocking'
|can be just as dangerous as 'overclocking' !!   Strangely, this appears to
be
|at odds with the documentation which suggests that running a cpu slower
|is the 'safe' option.

With those same Asus AMD motherboards we had quite a lot of problems with
new fast memory (fast for its time, and maybe cheap), which if you clocked
them down started behaving themselves.


-kristian
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