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SubjectRe: a question about p4_clockmod module on Xeon quad core processors
On Thu, Jan 29, 2009 at 03:27:24PM +0300, Michael Tokarev wrote:

> > p4-clockmod doesn't change the processor frequency.
>
> Hmm.. But what it really does, then?

it modulates the clock so the CPU isn't always availble for doing work.

> I used it one one machine which had a flaky CPU cooler,
> to reduce power consumption during hot summer days.

it reduces the amount of heat generated, by making jobs
take longer to finish. This comes at a cost of the CPU not
being able to enter lower C states for longer periods of time,
so you may end up actually using *more* power.

> It worked, and reportedly the frequency varied from
> 200MHz to the max of 2.4GHz (it's a P4 Xeon).

The CPU was always at 2.4GHz, even if it said '200MHz'.
It was just only doing work once in every 12 clocks.

Dave

--
http://www.codemonkey.org.uk


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