CPU Frequency scaling / Centrino

The required package (cpufrequtils) is installed by default if you selected "Laptop" package-set during installation.

First, you need to make sure the corresponding modules are loaded by default at boot time.

/etc/modules
        # Add the following lines to prepare cpu scaling
        speedstep-centrino
        # or add...
        #    acpi-cpufreq
        # ...instead of speedstep-centrino
        cpufreq_stats
        cpufreq_ondemand
        cpufreq_conservative
        cpufreq_powersave

Note that speedstep-centrino is deprecated as of kernel 2.6.20. Use kernel modue acpi-cpufreq instead.

Next, put the following in /etc/default/cpufrequtils, which may have to create first, if it doesn't exist.

/etc/default/cpufrequtils
        #Change Add this line to configure CPUs on bootup
        ENABLE="true"
        GOVERNOR="ondemand"
        MAX_SPEED=0
        MIN_SPEED=0

if you don't want to reboot, then modprobe the above modules and run:

invoke-rc.d cpufrequtils restart

Making sure it worked

To make sure it worked, you can issue the command cpufreq-info to find out about the current governor and speed of your CPU(s).