Re: [dwm] [OT] frequency scaling and power consumption

From: David Tweed <>
Date: Fri, 8 May 2009 10:38:11 +0100

On Fri, May 8, 2009 at 9:08 AM, bill lam <> wrote:
> BIOS support choosing a smaller multipliers to reduce cpu frequency.
> linux also supports frequency scaling such powernowd. Some google
> page said cpu throttling can not reduce power consumption. My
> experience is that it seems to lower temperature. If it can also
> reduce power consumption, I'm willing to save money by running cpu at
> half of its current frequency. Any idea.

My understanding is that power usage scales nonlinearly with CPU
frequency, and in particular having twice the frequency doesn't
require quite as much as double the power. So IF your OS can put your
PC into proper "sleep" states whent here's nothing to do (and that's
the big IF), the PC will use less energy in total by running at full
speed when you have work to do and then going into a sleep state
rather than taking twice as long to do the work at half the frequency.
So I'd expect you'd probably get more "energy usage reduction" from
getting rid of any services/device drivers/etc that stop the PC going
to sleep than from manually reducing the frequency. (If you're using
Linux, PowerTOP (

) is an attempt to provide a way to at least see what's causing
wake-ups, even if it doesn't necessarily show how to solve them.)
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cheers, dave tweed__________________________
computer vision reasearcher:
"while having code so boring anyone can maintain it, use Python." --
attempted insult seen on slashdot
Received on Fri May 08 2009 - 09:38:11 UTC

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