Re: Which cpufreq driver is best for ...

[Dominik Brodowski <linux@brodo.de>]

On Wed, Sep 03, 2003 at 07:57:49AM +0200, Norbert Preining wrote:
> Hi!
> 
> Which cpufreq driver is best for 
> 	Mobile Intel(R) Pentium(R) 4 - M CPU 2.20GHz
> I can use the
> 	p4-clockmod
> and the
> 	speedstep-ich
> With the p4-clockmod I can adapt the freq between 274MHz and 2.2GHz,
> while with speedstep-ich I can only go between 1.2GHz and 2.2GHz. So I
> guess p4-clockmod is superior for my chip/cpu.
No, speedstep-ich is "superior". p4-clockmod only "throttles" the CPU, i.e.
it scales down the frequency but not the voltage. This results in an
approximately linear saving of energy. speedstep-ich also scales the
voltage, which causes much better saving of energy. 

And as long as ACPI C-States "idling" or APM "hlt" instructions work, the
CPU is "throttled"[*] if there is no work to do anyway, so the p4-clockmod
driver doesn't save you anything. The p4-clockmod driver almost only is
useful where ACPI or APM "idling" is borken.

> In the same line - are there any new governors with `intelligent'
> scaling techniques.

Not yet. Stay tuned, please.

	Dominik

[*] I know, this isn't technically true. But it's a good approximation...