How does notebook vary speed of desktop CPU?

lee

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Hi,

Just curious to know?
How does my Toshiba 2450 manage to slow down it's *desktop* P4 CPU when
running on batteries?

It doesn't seem to be changing either the FSB or multiplier, yet the
machine is definitely slower when set to "optimize battery life" and
benchmarks show normal speed when set to "high" and lower figures for
"medium" down to roughly the speed of a P3 800 when set to "low".
Using a real-time clock speed checker, when running the benchmarks the
reported clock speed does not change from 2.8 Ghz

It *does* make a difference to battery life, so it must be doing
something, but what?

Lee
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> How does my Toshiba 2450 manage to slow down it's *desktop* P4 CPU when
> running on batteries?

It might be disabling cache, inserting wait states, or it might be
modulating, rather than actually varying, the CPU speed (e.g. running
at 2.8GHz but with only a 75% duty cycle).
 

lee

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Lee wrote:
> Hi,
>
> Just curious to know?
> How does my Toshiba 2450 manage to slow down it's *desktop* P4 CPU when
> running on batteries?

Ok, doesn't matter I found out it uses ACPI to do it.

Lee


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Lee wrote:
>
> Lee wrote:
> > Hi,
> >
> > Just curious to know?
> > How does my Toshiba 2450 manage to slow down it's *desktop* P4 CPU when
> > running on batteries?
>
> Ok, doesn't matter I found out it uses ACPI to do it.
>

And what is that?
 

lee

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Lewin A.R.W. Edwards wrote:
>>How does my Toshiba 2450 manage to slow down it's *desktop* P4 CPU when
>>running on batteries?
>
>
> It might be disabling cache, inserting wait states, or it might be
> modulating, rather than actually varying, the CPU speed (e.g. running
> at 2.8GHz but with only a 75% duty cycle).

Reading through the ACPI specs, this last point is explained and I think
that is what it's doing.
Interesting anyway ;)

Lee
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