fsb/ram divider

i'm interested in learning about overclocking. i've been reading all i can find on the subject. most of the terms i understand. one thing i can't figure out is this fsb/ram divider. i have an asus a8n-sli premium motherboard. when i go into the bios i don't find anything that is named that. thinking asus might call it something else i check the options for several different things and cannot find anything with any of the ratios ie 1:1,3/3,4/4,5/5 etc. can somebody explain this to me? thank you