🚀 go-pugleaf

On Wed, 17 Nov 1999 07:28:33 +0000, Oz <Oz@upthorpe.demon.co.uk> wrote:

>>If you overclock, How do you know that everything will work all the
>>time, in all circumstances, 
>
>Even if you don't, how do you KNOW this?
>You don't. Mostly because things don't always work all the time and in
>all circumstances whether guaranteed or not.

It's not quite as vague as that.  Semiconductor devices are specified to
work over a specified range of temperatures, supply voltages and, at the
external interfaces, limits of logic voltage levels and output currents. The
way in which the performance varies with these parameters is often quite
systematic and well known, so it is easy to define a few worst case
combinations of conditions, under which if a chip passes its tests you can
be confident that it will work uder all other combinations which are inside
the "recommended operating limits".  While these conditions are met, the
manufacturer can guarantee correct operation.  Note that "guarantee" is not
scientific proof that it will work; it indicates that the supplier can
afford to offer you your money back if it doesn't, because any remaining
failures will be rare cases of premature ageing due to random flaws in the
silicon, i.e. a quite different mechanism.

I was once told that Texas sorted their TTL devices into mil spec and
commercial spec by performing a single leakage current test, which
characterised the chip.  If that was within certain limits and the chip had
already passed a simple functionality test under normal conditions, they
knew the chip would work over the -55 to +125 degree temperature range and
4.5 to 5.5 Volts supply.  Within wider limits it would be OK fo 0 to +70 and
4.75 to 5.25 volts.

>Your argument is specious in the face of the overwhelming evidence of
>experience some of which has been posted to this thread.

That's unneccesarily strong.  There are systematic limits to the operating
conditions, and a chip as supplied and run at the correct clock speed and
other conditions is very likely to be reliable.

For any chip there will be a clock speed over which the error rate increases
dramatically.  That speed will of course be above the rated clock speed, and
(as discussed earlier) may sometimes be above the next standard step up in
clock speed too, if you are lucky.

In other words, at a given clock speed a given chip will either work or it
won't.  Of course that's not the only hardware reason why a PC may crash,
but that's another matter.

-- 
Anahata
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