CPU frequency scaling is implemented in the kernel under cpufreq
infrastructure. You can try searching online for information on that.
You could try looking for software in the Trisquel repositories to help you
do this. For example:
$ apt-cache search cpu frequency
You can search for any keywords you like. You can find tools that can allow
you to control voltage and frequency of your CPU, such as CPU frequency
daemons.
You should research this on your own. Search and read.
Follow the suggestions on the manual I linked to last time.
And be aware you may damage your CPU if you are not careful.
