"CBFalconer" <cbfalconer@yahoo.com> wrote in message
news:42F915FD.F63BD258@yahoo.com...
> kony wrote:
> >
> ... snip ...
> >
> > If you underclock a 400MHz CPU to 300MHz but leave the
> > voltage the same it will produce exactly same amount of heat
> > as a 300MHz CPU will, because they're actually the same CPU.
> > Sometimes there is a very minor deviation to this as very
> > slight core changes are made to facilitate higher clock
> > speeds in later models per CPU family, but generally
> > speaking the difference isn't worth much consideration.
>
> Not so, because the primary current flow mechanism is to charge and
> discharge many itty-bitty capacitors once per clock cycle. This
> results in a certain Q (coulombs) per clock period, and when you
> increase the period you decrease the net Q per unit time, which is
> current. Thus the 400 to 300 frequency ratio should result in 3/4
> the current draw, and thus 3/4 the power level.
>
Yes I would agree with that, posibbly or even better, however is not
power current squared X resistance in which case it wuld be
3/4 X 3/4 = 9/16 = about half the power?
If true thats quite a saving on heat and you might get away
without a heatsink even better to drop from 600 to 300
which would be only 25% of normal power.



> If you are comparing to a CPU rated at only 300, then it is
> obviously not the identical CPU for some reason or another. If it
> is built from the same masks using the same doping etc. it may very
> well act the same as the derated 400, but there is no guarantee of
> that. It may be derated because of some mechanism that prevents
> charging the capacitors fully in the shorter period, for example.

>
> --
> Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net)
> Available for consulting/temporary embedded and systems.
> <http://cbfalconer.home.att.net> USE worldnet address!
>
>