I've got 2x2 GB 1333 Mghz 1.65v + 2x4GB 1600 Mhz 1.5v. While on the MOBO said slots 0->4, i Inserted the 2 gb blocks into the Gray slots and the new 4gb blocks into the Black slots. Now it hows as if I put the old ram into the primary slots. Is this really the case or it doesn't matter as long as they are on the same colors ?