Trying to get homebrew running on your PSP? Want to add a screen light to your Game Boy? Trying to figure out how to work your GP2X? By popular demand, discuss it in here! (This forum is for pre-built handhelds, NOT custom made portables!)
If you underclock something, you give it a lower clock than it normally has.
For instance, if you underclocked a 2 GHz processor, you might haev a processor that runs at 1.5 GHz. Overclocking- same thing, just the opposite; 2 GHz -> 2.5 GHz.