Originally posted by Jrod
Why? Can you link me to some documentation of this?
I don't have any concrete sources, but word is RAM slot overpopulation can increase RAM latency. I'm almost sure I read in an article somewhere that when all slots are full, RAM downgrades to a 2T command rate. It makes sense if you think there's 4 modules (instead of two, for example) where data can be stored, so deciding which one to access takes some extra time - but I'm just speculating here.
I am sure, however, that some motherboards can't support their memory max speed when all slots are full (it'll downclock the memory).