Messages in this thread | | | Date | Thu, 29 Jan 2009 12:24:06 -0500 | From | Dave Jones <> | Subject | Re: a question about p4_clockmod module on Xeon quad core processors |
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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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