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SubjectRe: a question about p4_clockmod module on Xeon quad core processors
On Thu, Jan 29, 2009 at 11:40:25AM -0800, Xiaoning Ding wrote:

> Thanks for the explanation. So the conclusion is that ACPI-cpufreq
> can reduce power consumption by lowering cpu frequencies, and
> p4-clockmod can hardly save power because CPU frequences are not
> changed.

yes. and also that it inhibits entering deeper C states for longer periods.

> My experiments do not consider power consumption. It only requires to
> slow down the speed of some cores by either reducing frequencies or
> clock modulation. In such case, p4-clockmod is still a good choice for
> me. Can anyone give me some hints on whether p4-clockmod works on Xeon
> quad-core processors, and how to get it work?

I'm not sure if the registers are still there on quad cores, but I
would be surprised if they weren't. Hitting them directly with
msr tools is probably the best way, or writing a small program
that manipulates /dev/cpu/*/msr directly.

Dave

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


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