How to make use of Dynamic Frequency Scaling

general

Linux supports Dynamic Frequency Scaling for ThinkPads with mobile Pentium III, Pentium 4 and Pentium M processors.

configuring the kernel

2.4 kernels

Todo...

2.6 kernels

You need to enable the cpu frequency scaling for your kernel:

CONFIG_CPU_FREQ=y

The 2.6.x Debian kernel packages have this enabled already.

You need to load a governor:

set "CONFIG_CPU_FREQ_GOV_PERFORMANCE=y"
set "CONFIG_CPU_FREQ_GOV_POWERSAVE=y"
set "CONFIG_CPU_FREQ_GOV_USERSPACE=y" or load module "cpufreq_userspace"

since 2.6.10 there is the ondemand governor in the kernel

In Debian kernels it should all be available as modules.

• You need the userspace governor to have a userspace daemon (see below) do the frequency scaling. Since 2.6.10, there is also the ondemand governor in the kernel, which replaces any userspace daemon for cpu scaling and works very well.

• If you have a Coppermine-piix-smi based Thinkpads like from the A2x, X2x and T2x series you need to enable the speedstep-ich driver in the kernel and load it if it's built as module. You might want to look at this page.

• If you have a p4-class celeron based Thinkpad like the R40e you might want to look at this page

configuring SpeedStep daemons

To use any of the following user space frequency scaling daemons you need to load the module:

• cpufreq-userspace

There are plenty of userspace frequency scaling daemons available:

• cpufreqd
• cpudynd
• speedfreqd
• powersaved
• powernowd