Looking for a work around here.

Asus A7N8X MB
Barton AMD 2800/333
512MB DDR400

Right now I have the multiplier set on 12.5 and FSB set at 168 = 2,100.

I would like to up the multiplier to 13 or higher to overclock, but when I set multiplier to 13, speed says 832mhz. I read this is a problem on some Nforce 2 MB. Anyone know any work arounds without having to do anything to cpu?