First: Install gnome-applets in order to get cpufreq-selector application.
sudo apt-get install gnome-applets
*NOTES: gnome-applets installs a LOT of stuff and will take more than 300MB of free space.
Second: Check if your CPU supports frequency scaling
*NOTES: It will take a few seconds or more to finish. If it doesn’t return any output proceed to the next step. If you get this message “No cpufreq support” then do not follow the next steps as you will not find neither the files mentioned below nor work out this way for you.
Three: Find out the available frequencies that your system can scale to and the available governors (modes of operation for frequency scaling).
*NOTES: You will get output that resembles these: 3000000 2300000 1800000 800000 and conservative ondemand userspace powersave performance.
Four and final step: Configure your system one core at a time.
sudo cpufreq-selector -c CORE_NUMBER -f FREQUENCY_IN_MHz -g GOVERNOR_MODE
*NOTES: CORE_NUMBER: An integer value that defines the core you want to edit. FREQUENCY_IN_MHz: A frequency from the scaling_available_frequencies file. GOVERNOR_MODE: A mode name from the scaling_available_governors file.