I was at the Apple store yesterday with the need to run both my CPU's at max for some tests. The "Genius" put the following in two separate Terminal windows
Yes > /dev/nullThe YES commandsimply sends an endless stream of y’s to standard output until killed. The reason the guy did it twice is to ensure that both CPU's are being used. This should work on any *nix machine but if you only have 1 CPU you only need to do it onceIf are even to lazy to open two windows you can just put the following in one:
Yes > /dev/null & Yes > /dev/null