My Corsair PC 2700

I have a P4b533 motherboard (asus) with some good xms corsair pc2700 memory. I cant push up my fsb any more due to my processor - (at 140 FSB already-1.8a processor). My memory is only running at 280 mhz. How can i get it up to 333 mhz like pc 2700 is supposed to do? I know u can use ratios and the such, but i think in my bios all i have to select between is 1:1 and 4:3 (or 3:4). All i know is that in 3d mark the 1:1 yielded better results than the the 4:3
Thanks

Set your memory setting to auto.

synchronous settings always yield greater results (1:1) than async (any other besides 1:1)