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

[Xiaoning Ding <dingxn@ymail.com>]

I installed msr-tools, but could not find detailed information on how to change cpu speed with the tools. Can you point me to detailed documentations? Or, can you share your code?

Thanks!

Xiaoning

--- On Wed, 1/28/09, Wes Felter <wesley@felter.org> wrote:

> From: Wes Felter <wesley@felter.org>
> Subject: Re: a question about p4_clockmod module on Xeon quad core processors
> To: dingxn@ymail.com
> Cc: linux-kernel@vger.kernel.org
> Date: Wednesday, January 28, 2009, 9:05 PM
> 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@felter.org