cpufreqd is meant to be a replacement of the speedstep applet you 
can find on some other OS; it monitors cpu usage, battery level, 
AC state, and running programs and adjusts the frequency governor 
according to a set of rules specified in the config file.
You need a CPUFreq driver and either APM, ACPI (a recent version) 
or PMU enabled in your kernel config in order for this deamon to work.

You will also need to have the cpufrequtils package (which includes 
libcpufreq) installed in order to build cpufreqd, and cpufreqd can
make use of libsensors and/or nvclock if you have them installed -
see the documentation included with the source tarball for more details.
