Re: Status of X86_P4_CLOCKMOD?

[Dave Jones <davej@redhat.com>]

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