[Bug 177646] Re: Celeron M530, no frequence scaling

[Matthew Garrett]

Yes. If you use p4_clockmod, you can alter the frequency of the
processor. However, you cannot alter the voltage. As a result, you can
reduce the power consumption of your processor by around a third only by
making it take twice as long to do anything. This does not save you
power overall.

C states allow the processor to unclock itself and save significant
quantities of power by disabling unused portions of the CPU. They are
automatically used on Linux, even on the Celeron. However, they can only
be entered if the processor is entirely idle. If you use p4_clockmod
then your processor will spend more of its time working and less time in
the C states. As a result, it will consume more power than if you don't
use p4_clockmod.

HMC8: Modern Intel processors only support reducing the core voltage
(which can reduce power consumption) if they have "est" in their flags
field. Otherwise, it's better to run at full speed in order to allow
earlier entry to the C states.

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Celeron M530, no frequence scaling
https://bugs.launchpad.net/bugs/177646
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