You can Manually set the governor by running the cpufreq-set command (as root).
Just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the commands below.
sudo cpufreq-set -c 0 -g ondemand
To install cpufreq:
sudo aptitude install cpufrequtils
cpufrequtils includes a daemon which allows users to set the desired scaling, governor and min/max clock speeds for all processor
cores at boot-time. Before starting the daemon, edit
/etc/conf.d/cpufreq as root, selecting the desired governor and
setting the min/max speed for your CPU(s), for example:
#configuration for cpufreq control
# valid governors:
# ondemand, performance, powersave,
# conservative, userspace
# valid suffixes: Hz, kHz (default), MHz, GHz