linux-kernel - Re: a question about p4_clockmod module on Xeon quad core processors

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Message-ID: <4980C8A9.6090904@felter.org>
Date:	Wed, 28 Jan 2009 15:05:45 -0600
From:	Wes Felter <wesley@...ter.org>
To:	dingxn@...il.com
CC:	linux-kernel@...r.kernel.org
Subject: Re: a question about p4_clockmod module on Xeon quad core processors

Xiaoning Ding wrote:
> Hi list,
> 
> I have tried the p4-clockmod module in Linux kernel 2.6.29 on Xeon 5355 quad-core CPUs with no luck. It seems current p4-clockmod driver still cannot support Intel Quad core processors, right? 
> 
> I know I can also use acpi-cpufreq. It can only scale down the frequence from 2.67GHz to 2GHz. But I need some lower frequencies for some experiments.

Clock modulation is quite simple; in the past I've done it from 
userspace with /dev/cpu/*/msr or written my own module to do it. I don't 
know if I've ever tried it on quad-cores, but it worked on dual-core 
Woodcrest. (Note: I was not trying to save energy.)

Wes Felter - wesley@...ter.org
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