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SubjectRe: Status of X86_P4_CLOCKMOD?
On Sat, Feb 25, 2006 at 02:57:22AM +0100, Johannes Stezenbach wrote:
> On Thu, Feb 23, 2006, Dave Jones wrote:
> > On Thu, Feb 23, 2006 at 08:59:37PM +0100, Adrian Bunk wrote:
> > > 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.
>
> Doesn't less heat imply less power consumption?

Not really. The only energy you're saving is that your CPU fan
will turn slightly slower, which is probably going to be < 1W
of difference. Generated heat drop in a large room of servers
*may* mean the aircon has less to do, but I'd be surprised if
it made a noticable difference.

> - after some minutes of idling without user activity
> go into lowest power mode (could be triggered
> from xscreensaver)
> - at the slightest hint of user activity or CPU load jump
> back to max performance mode
> (- optionally use intermediate clock mod steps for
> non-interactive loads, but I'm not convinced it's
> worth it)

You should be able to modify cpuspeed or some other userspace
governor to do this quite easily.

Dave

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