Re: battery life with cpufreq

Fred Blaise
2005-09-19T11:39:49Z

On 9/19/05, Dominik Brodowski <linux-X3ehHDuj6sIIGcDfoQAp7OTW4wlIGRCZ@public.gmane.org> wrote:
> > Hi,
> > ok, it's clear. But isn't it true that in the periods with clock stopped
> > the CPU consumes much less power than in those with clock running ?
>
> Yes, indeed. However, it consumes exactly the same amount of energy as if it
> were in an "idle state" (ACPI C-States). And that's entered automatically if
> there is nothing for the CPU to do. As a typical CPU in a typical notebook
> only has something to do for 5% of the time, throttling to 75%, for example,
> means the CPU is:
> working 5%
> idling 20%
> throttling 75%
>
> moving "time" around from idling to throttling or the other way around
> doesn't matter anything. If you use CPU frequency scaling, though, the
> "working" part consumes less CPU power. Also, the "idle state" typically
> consumes less power if the CPU frequency and voltage was scaled down.
To sum up, I am screwed I guess :\ Since the speedstep* don't work for
me... No long battery life for me...

Thanks for your explanations.
>
> Dominik
fred