A free app for Android, by Mugich CPU Tools.

CPU Performance Control is a tool for people who want to manage their device’s processor or core. It allows you to choose the frequency and the governor independently for each. It also lets you check the state of each core in real-time.

The tool has a number of options you can use to improve your device’s performance. You can use the highest frequency for all the cores to gain FPS in games, or you can go down to the lowest frequency and decrease power consumption when your phone is sitting idle.

The Multi-core CPU Control mode can only work without other platforms or services running in the background.