My problem is that I want to take advantage of using the quad-channel by using 4 slots, but slots DIMM_A1 and A2 are currently not available because I'm running a Corsair H50 in push/pull setup and the radiator/fans don't allow enough room for the RAM. I could use low-profile ram, but it's ridiculously expensive. I'm currently using Corsair Vengeance and the heat spreaders are a bit too tall to fit and I won't be able to use the recommended config.
So what I'm wondering is if I could use slots DIMM_A1 and A2 and slots DIMM_D1 and D2. Would this be a problem? If so, why? I really don't know a whole lot about this kind of stuff and would be interested as to why certain configs may be better.
Thanks for your reply, but this mobo has 8 channels....so only 4 need to be used to have quad channel. I understand how that part works. What I'm asking is, does it matter which specific slots are used? The Asus manual seems to specify a very particular configuration.
Yes, it has two pairs of 4 channels. To use quad channel you have to place one stick in each slot marked A B C and D, and as far as I know, for X79 it has to be first one, for first 4 modules, meaning that they have to be placed in A1, B1, C1 and D1. Then they will work in quad channel. You can add second kit to A2, B2, C2, D2 later and it will be working as second set of quad channel memory, thus allowing you to use another modules (different capacity) than in first set.
You can't place modules for example in B1, B2, D1, D2 and have them working it quad channel. They have to be in slots of the same color. So if you have A1 and A2 blocked there is no way to utilize quad channel.