I think this applies to all Asus motherboards, but how do you tell if your memory is running 5:4, 3:2, or 1:1? I read it a while ago, but didn't pay much attention.
You can use cpuz (http://www.cpuid.com/download/cpu-z-120a.zip) to see what ratio you are using after you install the program in windows. I don't have an asus board, but I'm sure it states in the manual where to go in the bios to set it. Abit boards are set in the same screen where you set the fsb for your cpu.
Its not a matter of knowing where the settings are, just what they are. On the Asus boards they're labeled differently than 5:4, 3:2, and 1:1. Thanks for the link.