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SubjectRe: HELP: cpufreq on HT and/or SMP systems
Date
On Thu, 31 Jul 2003 23:53:54 +0200, Ricardo Galli wrote:

> I have some doubts regarding cpufreq for SMP systems (for developing
> http://mnm.uib.es/~gallir/cpudyn/).
>
> If I remember well, I read a while ago that cpufreq didn't work in SMP
> systems, but reading the docs and kernel/cpufreq.c, it seems there should be
> any problem?
>
> Is it true?
>
> OTH, I trying it on a P4 HT, and it works, changes in the frequency of one of
> the "cpu's", changes both.

That makes sense, since the CPU only has one clock.

> What happens in the case of several real cpu's? Does it keep the same
> frequency for every cpu? According to a comment in cpufreq.c, it seems that
> each cpu might have different frequencies.

AFAIK no SMP systems have voltage/frequency scaling (SpeedStep/PowerNow).
I've heard that ACPI P-states works on SMP, but if it's not doing
voltage/frequency scaling then I don't know what it's doing.

Wes Felter - wesley@felter.org - http://felter.org/wesley/

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