Re: battery life with cpufreq

[Fred Blaise <chapeaurouge-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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)
> 
> "In contrast to CPU frequency scaling, where the operating frequency is
> constantly modulated, throttling means the CPU is forced to a halt for short
> periods of time. If throttled, the CPU [enters] into a physical and
> electrical state comparable to the idling states mentioned above, so it can
> be described as an enforced idling of the CPU.
> 
> As certain CPU power state typically utilize similar hardware
> implementations, and as throttling does not have a positive effect on the
> energy consumption during CPU power states, throttling the CPU by a given
> rate is only useful if the CPU is less idle than the throttling rate."
> 
>         Dominik
>


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