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SubjectRe: Status of X86_P4_CLOCKMOD?
On Thu, Feb 23, 2006 at 03:41:10PM -0500, Dave Jones wrote:
> On Thu, Feb 23, 2006 at 08:59:37PM +0100, Adrian Bunk wrote:
>
> > > > > config X86_P4_CLOCKMOD
> > > > > depends on EMBEDDED
> > > >
> > > > This one is an x86_64 only issue, and yes, it's wrong.
> > >
> > > That's for P4, not X86_64... And since P4 clock modulation does not provide
> > > almost any energy savings it was "hidden" under embedded.
> >
> > But the EMBEDDED dependency is only on x86_64:
> >
> > arch/i386/kernel/cpu/cpufreq/Kconfig:
> > config X86_P4_CLOCKMOD
> > tristate "Intel Pentium 4 clock modulation"
> > select CPU_FREQ_TABLE
> > help
> >
> > arch/x86_64/kernel/cpufreq/Kconfig:
> > config X86_P4_CLOCKMOD
> > tristate "Intel Pentium 4 clock modulation"
> > depends on EMBEDDED
> > help
> >
> > And if the option is mostly useless, what is it good for?
>
> It's sometimes useful in cases where the target CPU doesn't have any better
> option (Speedstep/Powernow). The big misconception is that it
> somehow saves power & increases battery life. Not so.
> All it does is 'not do work so often'. The upside of this is
> that in some situations, we generate less heat this way.

This is perplexing. Less heat equals less power usage according to the
laws of thermodynamics.

--
Mathematics is the supreme nostalgia of our time.
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