host clk vs. by speed

i've got a shuttle ak31 v2 mobo, and it gives me the choice to set the ram to host clock or "by speed." if i'm not mistaken that means that it can either run at the speed you set it to or it can go by whatever the fsb is set to. is that true? and if it is, which is which?

I am not very positive about this, but I think "host clock" is using whatever the fsb is at (135fsb, then your mem is running at 270mhz) and "by speed" is using the default of the mem, so it's running at 266mhz

or it may be +33MHz if you are using a 100MHz fsb

cool, that's what i wanted to know . . . thanks, guys!