I don't think that I understand your question. Instead of me babbling on about something that I don't have that great of an understanding of, I think that this site might be able to clarify a few things for you. It was one of the first that came up on Google (that seemed reliable).
http://www.hardwaresecrets.com/understanding-ram-timings/
There is a Wikipedia page too, but you shouldn't trust everything you read there.