Re: battery life with cpufreq

[Dominik Brodowski <linux-X3ehHDuj6sIIGcDfoQAp7OTW4wlIGRCZ@public.gmane.org>]

Hi,

On Mon, Sep 19, 2005 at 11:35:24AM +0200, Fred Blaise wrote:
> On 9/19/05, Dominik Brodowski <linux-X3ehHDuj6sIIGcDfoQAp7OTW4wlIGRCZ@public.gmane.org> wrote:
> > Hi,
> > 
> > On Mon, Sep 19, 2005 at 11:11:01AM +0200, Fred Blaise wrote:
> > > I have an dell inspiron 5150, 3Ghz. I have loaded p4_clockmod, and my
> > > CPU frequency now changes with powernowd. It seems to work well.
> > >
> > > However, I am not seeing any battery life improvement.
> > >
> > > Any ideas?
> > 
> > Yes. In general, throttling doesn't improve battery life, only CPU frequency
> > scaling does:
> ok.. So the fact that my CPU goes down to 383Mghz instead of the
> normal 3Ghz is not frequency scaling? (pardon the noob that I am if
> this question doesn't make sense)

Exactly. In fact, the frequency rate is not changed, it is only stopped for
short periods of time.



3 Ghz	  	  :	x x x x x x x x x x x x x x x x
scaling to 1.5 GHz:	x   x   x   x   x   x   x   x 
throttling to 1.5 :	x x x x       x x x x         x
			-------------------------------> t
			[x] denotes an instruction is executed by the CPU

If either the acpi-cpufreq or one of the speedstep-* modules works, you
should use that instead of p4-clockmod -- these offer (under normal
circumstances) CPU frequency scaling, while p4-clockmod only offers
throttling.

	Dominik


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