[Vacillator]

It supposedly tells the program which core of your processor to use (1 or 2 for dual core or 1, 2, 3 or 4 for quad). There has been debate about whether it makes any difference - perhaps if one core is 'busy' with something in the background it might help? Personally mine is set to 1 and setting it to 2 made no noticeable difference.

EDIT: Oops got the numbers wrong! See below.