On Tue, Feb 28, 2006 at 01:46:29PM -0600, Matt Mackall wrote:
> 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.
you end up taking longer to do the same amount of work, so you
end up using the same overall power.
Dave
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