Just compile and run it - it has extensive online help ;) Be aware that this utility only supports Intel Pentium III Mobile-M cpus, on all other models/cpus, it might kill your data or fry your machine. Check /proc/cpuinfo, it should look like this: model name : Intel(R) Pentium(R) III Mobile CPU 1000MHz Normal P-III's (Pentium III (Coppermine)) don't work. Please note that only 82801CA und 82801BA chipsets work, and then only some of them. There is a project that tries to much better integrate speedstep into the linux kernel, maybe it works much better than this utility. Please go and have a look: http://www.arm.linux.org.uk/cvs A list of Notebooks that don't seem to work so far is (please feel free to send any additions/corrections): HP Ombibook XE3 Dell Latitude C610 Dell Inspiron 4100 Please also note that this program might trash everything your kernel ever thought about timekeeping... The newest version will soon be available at http://speedstep.plan9.de/ The options should be self-explaining (anybody care to write a manpage? ;), except daemon mode. In daemon mode, the program checks each second wether the cpu is busy (user time + system time, idle processes are NOT counted), i.e. 90% of the timeslices were used in calculations and puts the cpu in maximum performance mode. If the cpu is relatively idle for 6 seconds, battery optimized mode will be enabled. The actual constants may be edited in speedstep.c (sorry ;)