[Grml] Controlling CPU Frequency

Michael Prokop mika at grml.org
Tue Jul 31 08:47:32 CEST 2007

* - Tong - <mlist4suntong at yahoo.com> [20070731 03:15]:

> I rebooted my PC the other day, and only then I know that my CPU is
> overheated, because I saw a BIOS warning. The fact that my CPU might have
> been overheated for months made me consider seriously to control my CPU
> frequency (My AMD cpu has that feature available in bios).

What temperature was your CPU running at?

> I've tried to make use powernowd before, but never able to. I should feel
> lucky this time since the latest kernel that grml 1.0-1 uses, support cpu
> frequency control by default:

> http://kernelnewbies.org/Linux_2_6_20
> "Grand unification of ACPI based speedstep-centrino and acpi-cpufreq
> drivers. It combines functionality of these two driver into acpi-cpufreq
> driver."

> But the problem is that googling "acpi-cpufreq" didn't come up much
> result. The closest is from
> http://bbs.archlinux.org/viewtopic.php?pid=256607

> "... you should try the 'acpi-cpufreq' module. My favorite governor is the
> 'conservative' one.  Under load, it will ramp up the frequency, but it will
> generally keep it as low as possible."

> But there is no details. So I'm wondering if anyone can help me here?

acpi-cpufreq is the kernel module used instead of speedstep-centrino
with kernels >=2.6.20.

To check your current settings regarding cpu frequency scaling check
output of 'cpufreq-info'. To configure your current settings (if you
aren't happy with the defaults) either manually use sysfs or use the
userspace tool cpufreq-set.

Is the 'thermal' kernel module loaded on your system? Check CPU
temperature using tools like sensors/mbmon (depending of your
hardware whether what's supported of course).

If you want to read some docs regarding ACPI and cpufreq start for
example with
https://www.linux-magazine.com/issue/40/ACPI.pdf and
https://ols2006.108.redhat.com/2007/Reprints/brown_1-Reprint.pdf and
the docs inside Documentation/cpu-freq/ of current kernel sources.

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