Undervolting a pentium M with speedstep-centrino

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Undervolting a pentium M with speedstep-centrino

Postby kilou on Sun Jul 13, 2008 2:13 pm

Hi,

I'm using Elyssa on my laptop and would like to undervolt my CPU using PHC. I've seen many HowTo to do this with the acpi-cpufreq module but my CPU is using the speedstep-centrino module. Does anyone know if there is a patch for the speedstep-centrino module or is it possible to use the acpi-cpufreq module on a Pentium M (Sonoma)?

If I need to compile a kernel for this to work I will need to use a vanilla kernel. Is there any problem using a vanilla kernel in linux mint? Will I loose some functionalities? What are the specific Mint options in the kernel?

Thanks
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Re: Undervolting a pentium M with speedstep-centrino

Postby Husse on Tue Jul 15, 2008 7:11 am

This link seems to have some info on the subject
http://marek.havlickovi.com/?p=6
It was however down when I tried to connect
And google is your friend
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Re: Undervolting a pentium M with speedstep-centrino

Postby Lord Platin on Tue Jul 15, 2008 7:44 am

Your CPU should work with acpi-cpufreq, you only need to add "blacklist speedstep-centrino" to /etc/modprobe.d/blacklist and your kernel will automagically use acpi-cpufreq :)
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Re: Undervolting a pentium M with speedstep-centrino

Postby kilou on Tue Jul 15, 2008 3:03 pm

@Husse: this link concerns only CPU that work with acpi_cpufreq such as Core Duo/Duo2 but not earlier generations of Pentium M like Sonoma or Dothan. Mine is a Sonoma (single core) and it uses speedstep-centrino.

@Lord Plain: I tried to add "blacklist speedstep-centrino" to /etc/modprobe.d/blacklist and it effectively prevents the speedstep-centrino module to load after a reboot. However acpi-cpufreq module is not loaded automatically and even if I type sudo modprobe acpi-cpufreq to load it manually I get:

FATAL: Error inserting acpi_cpufreq (/lib/modules/2.6.24-16-generic/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko): Device or resource busy

Any solution to that? Indeed it would be perfect if I can load acpi-cpufreq :P

EDIT: with speedstep-centrino blacklisted, I can load acpi-cpufreq but first I have to manually unload speedstep-centrino with sudo modprobe -r speedstep-centrino. Then I can load sudo modprobe acpi-cpufreq and it works. It seems that blacklisting speedstep-centrino makes it uneffective but it's still loaded.

Is there a way to force speedstep-centrino to not load at startup and load acpi-cpufreq other than with a script??? That would do the trick.

EDIT2: seems like adding acpi-cpufreq to /etc/modules loads it at startup and it works with speedstep-centrino blacklisted.
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Re: Undervolting a pentium M with speedstep-centrino

Postby Lord Platin on Tue Jul 15, 2008 5:15 pm

Of course, sorry, seems like I'm getting too used to distros doing all the work for you ;)
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