Monday, February 18, 2008

AMD Frequency Scaling

The Amd Turion 64 X2 can run at various speeds and it can scale up or down dinamically.
This primarly a power saving and power consumption optimization.
This charts shows the available frequencies this processor can run with.

analyzing CPU 0:
driver: powernow-k8
CPUs which need to switch frequency at the same time: 0 1
hardware limits: 800 MHz - 1.80 GHz
available frequency steps: 1.80 GHz, 1.60 GHz, 800 MHz
available cpufreq governors: conservative, ondemand, userspace, powersave, performance
current policy: frequency should be within 800 MHz and 1.80 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 800 MHz.

New Linux Kernels should have this kernel module install by default, but old ones like mine was had to be recompiled to include the module.
Amd also provides a Power Monitor and some cpu frequency governors by default.,,30_182_871_14098,00.html

I mostly use ondemand, that is it scales up or down according to the needs for processing the system has. For instance it is running at 800 Mhz as i write this but it quickly steps up to 1.8 when i put some source to compile.

Powersave uses the lowest power consuming option and performance the highest.

You can use the cpufreq-utils in the debian repos to find out more about your own processor.

It considerably reduces battery life when you have this daemon running so if you use an old kernel (< 2.6.16), you might have to update or recompile.

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