When it came to overclocking on the ASUS Crosshair III Formula, I found it easier and more effective to push the BUS speed versus raising the multiplier. When raising the multiplier, I was only able to push it to 18x for a total speed of 3.6GHz before I lost stability. However, by putting the voltage to the maximum of 1.5v, I was able to push the BUS speed all the way to 241MHz for a total overclocked speed of 3.854GHz, which is over 200MHz more than the previous attempt. With this stable speed, the overclocked settings will be run at 241x16 for 3.85GHz.

http://www.overclockersclub.com/reviews/crosshair_iii/