Is there a way to adjust the memory divider on a X58 Extreme mb? I want to be able to fine tune my oc.

i7 920 oc 3.567 (21*170) all voltage settings on auto
Noctua DH-14 cpu cooler
Asrock X58 Extreme mb bios P2.8
Corsair Vengeance 12gb 8-8-8-22 1T
2-Sapphire 5870 video cards crossfire
Corsair hx1000 power supply
Cooler Master Sniper Black case

thanks
1mrdad