Ahh what the snuff...I guess I closed the window on this instead of hitting reply or somethin lol
Depends on the mobo man, what are you using?
The MSI Neo2-Platinum was anal with the slots, and depending on the slots depended on dual channel working or whether or not it'd be DDR400 or limit it to DDR333
1&3 should be your safe bet, with 2&4 you'd need to read the manual just to make sure