Using ‘rdtsc’ to measure performance by counting CPU cycles is only useful if the CPU’s clock frequency is stable. In Ubuntu 10.04, right click a panel (e.g., the menu bar at the top of the screen) and click “Add to Panel…”. Select “CPU Frequency Scaling Monitor”. It will now appear on the panel. Click it with the left mouse button. The options should be self-explanatory. No word yet on whether settings persist across reboots (i.e., how to change the default).
One thread suggests the following:
create the file /etc/default/cpufrequtils
Inside it, place the following, obviously, change the governor and/or speeds you wish to use. When you reboot, cpufreq will read this file to determine your chosen settings. FYI: Setting speeds to 0 will set max and min to whatever your CPU supports, respectively.