Information about CPU Frequency Scaling.
From the CPUFreq home page:
Clock scaling allows you to change the clock speed of the running CPU on the fly. This is a nice method to save battery power, because the lower the clock speed, the less power the CPU consumes. CPU Freq is a generic framework to make architecture implementation specifics transparent to a user. Currently, CPU Freq supports various ARM CPUs (Integrator, SA1100, SA1110), various x86's (AMD Power NOW, VIA Cyrix Longhaul), and various Super H CPUs (SH-4 7750/7751, SH-3, and so forth). This project also incorporates some work at reverse engineering support for Intel Speedstep technology.
- CPU Freq home page: http://www.advogato.org/proj/CPUFreq/ (it looks a little out-of-date)
- Source Forge project for cpufreqd: http://sourceforge.net/projects/cpufreqd/
- LWN.net article pointing to Documentation post for 2.5.32 kernel: http://lwn.net/Articles/8642/
- Documentation is available in the source tree
- <kernel.org 2.6 linux>/Documentation/cpu-freq/*
- patches are available at: http://www.codemonkey.org.uk/projects/cpufreq/
The code in the CELF tree doesn't bear much resemblance to the current patches. Note that this whole system appears to be a backport of this feature from the 2.5/2.6 kernel version.