I recently accidentally found a nifty app for Linux; CPU Frequency Scaling Monitor by Carlos Garcia Campos. Known as wmsmpmon in apt and Synaptic Package Manager, the name is somewhat misleading. There’s another feature that is incredibly useful. This app allows you to lock your cpu(s) to specific speeds, provided your cpu supports speed stepping. YMMV.
Since I use a laptop, if I’m connected to AC, I force my cpu’s to top speed. If I’m running on battery, I force the cpu’s to lowest speed, and thus extend my battery life to some degree.
Definitely added to my “must-have” list of apps!