[ltp] speedstep useful ?

[Tino Keitel]

On Tue, May 22, 2007 at 08:16:34 +0200, Frédéric BOITEUX wrote:
> 	Hello,
> 
>   I've recently bought a Thinkpad X31 and installed a Debian Etch on
> it. It's my first laptop, and Debian Etch + ThinkWiki is a *very nice*
> way to have a full usable portable Linux computer !
> 
>   One thing I wonder is whether the Speedstep system is really useful
> or not : The Debian Etch didn't installed the speedstep_centrino nor
> cpufreq_* modules, and the BIOS seems to put the processor in full speed
> when on AC power and in low speed on batteries. Furthermore, I've tried
> to install the modules and the gnome cpufreq applet, and this applet
> don't react/blocks when the speedstep module is loaded.
>   Is it a reason speedstep_centrino isn't loaded at boot time by Debian
> system ?
>   Does loading it can help in some way ? The only use I see is to
> reduce cpu speed when idle on AC power to reduce heat : correct ?

Speedstep-centrino was made obsolete by speedstep-acpi
(CONFIG_X86_ACPI_CPUFREQ), so you might check this, if it is not
already loaded.

And yes, IMHO it is also usaful when on AC power, too, as it helps your
notebook to stay cool when the CPU is idle.

But loading the speedstep driver alone does not clock down the CPU. You
need a governor that does this (e.g. the ondemand governor) and
activate it, or use the userspace governor and let some userspace
program handle it. I prefer the ondemand governor. See the
cpufrequtils package to conigure this automatically at bootup.

Regards,
Tino