We briefly discussed overclocking in our Android rooting guide, but today we're taking a closer look at SetCPU, the app that makes it happen—as well as other ways to use it.
If you've rooted your phone (and most of you have), you can download SetCPU from the market and use it to set your CPU's clock speed. This is useful if you have an older phone and would like to make it run a little faster, or if you have a newer AMOLED phone with an unnecessarily beastly processor and want to slow it down to save precious battery life.
One of SetCPU's coolest features, apart from the basic clock speed setting, is profiles. You can tell SetCPU to set your clock speed based on any number of characteristics. For example, you could have your phone at full clock speed when your battery is over 50%, but underclock it when it is closer to dying (if you don't want to overclock it all the time). You can also set it to return your phone to its regular clock speed if the CPU temperature gets too hot, and give this profile priority over others so you make sure your CPU doesn't overheat. It's very useful, and helps you get the best possible experience out of your phone, whether it's old and slow or new and blazingly fast.
SetCPU is a $1.99 download for Android devices. Droid users will need a previously mentioned custom kernel, and Evo/Incredible/Desire users will need to hit SetCPU's menu and go do Disable Perflock.
SetCPU [via Jeremy O.S. Hindle]