This site for most detailed inquiries on overclocking:
www.overclock.net
Usually, I think the CPU multiplier is set to its highest level, and it doesn't have much reason to tone itself down. What you're looking for to make that multiplier better is changing the FSB (Front-side Bus) speed. If it's, say, 400 Mhz, and your multiplier is 5, then you get 2.0 Ghz. You won't be able to turn up the FSB so far, but it may make a difference. All I know is, be careful, and do it in increments to see how the system responds.