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Date:      Tue, 14 Jan 2003 15:00:57 -0800
From:      Peter Wemm <peter@wemm.org>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        John Baldwin <jhb@FreeBSD.org>, Wilko Bulte <wkb@freebie.xs4all.nl>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org, Nate Lawson <njl@FreeBSD.org>
Subject:   Re: cvs commit: src/sys/dev/acpica acpi_cpu.c 
Message-ID:  <20030114230057.81B422A89E@canning.wemm.org>
In-Reply-To: <20030114173224.A74488@grasshopper.cs.duke.edu> 

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Andrew Gallatin wrote:
> John Baldwin [jhb@FreeBSD.org] wrote:
> > aggressive policies in the future.  You could change the speed on
> > your desktop by changing the performance speed to be 6 (75%) using
> > the sysctl for example:
> 
> The scary thing is that for my destop setup, I can turn my speed down
> to 25% on my P4 and not really feel a difference in xterms, editors
> and soforth. (I CAN see a difference, I just don't mind it much).
> 
> Any idea about how much power this actually saves on a desktop?

FWIW, we see a (measured) difference of about 50W on 2.2GHz P4's simply by
turning machdep.cpu_idle_hlt on and off.  I expect the clock throttling
would make similar differences.  For 1U rack-mount systems (especially in
California) this is a Big Deal.

Cheers,
-Peter
--
Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com
"All of this is for nothing if we don't go to the stars" - JMS/B5


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