I use a Dell Dimension 3000 at home. It has a 2.8Ghz Pentium 4 so it generates a  bit of heat and power usage. I generally tend to enable CPU frequency scaling on any computer I use. So I went through the normal procedure I use. First:

kwame@amaterasu:~$ sudo dpkg-reconfigure gnome-applets

Select yes when I’m asked if I want to allow cpufreq-selector to run with root priveleges.

Then I add the CPU Frequency Scaling Monitor applet to the panel. I then select my desired scaling governor or speed and voila!

Not so with this computer. For some reason, it decided that “CPU frequency scaling is unsupported”. Turns out the kernel module for frequency scaling was not being loaded. So, it was off to the commandline:

kwame@amaterasu:~$ sudo modprobe p4_clockmod

Depending on your processor, you might have to change the module. See below.

Pentium 4, Celeron D, Pentium D, Celeron M : p4_clockmod
Pentium M, Core Duo, Core 2 Duo: speedstep_centrino
AMD K6: powernow_k6>
AMD K7 (Athlon, Duron, Sempron 32): powernow_k7
AMD K8 (Athlon 64, Turion 64, Sempron 64, Opteron 64): powernow_k8
None of above: acpi_cpufreq (may or may not work!)

Next is to load a module for your policy governor- which is a rule that determines how the scaling is carried out.

kwame@amaterasu:~$ sudo modprobe cpufreq_ondemand

There are 4 governors I know about – ondemand, performance, conservative and powersave. To load the appropriate module, you do a modprobe cpufreq_<nameofgovernor>.

Once that is done. I remove the CPU Frequency Scaling Monitor applet and add it again. Now that’s better.

One more thing to do. Use your favorite editor to open up /etc/modules and add the modules you used, each to a line and save. Now when you boot up, everything should be fine and dandy.

NB: The commands  were meant for a Dell Dimension 3000 but you should be to tweak them for your own setup. Remember,  ask for clarification when in doubt . You can probably get some more details from PolishLinux.