will not work mosie, you need with 2 cpu's in mobo also with each cpu to put mem in.
will not work when you have 2 cpu's and only on side of 1 cpu mem modules.
When i mean 6mem modules, i mean in the red slots with each cpu in bank 1, 3 and 5.
As for the downclocking, i mean when you are running two cpu's, and put ALL mem banks full (all 12 slots), the IMC is limiting factor.
don't think with 48gb of ram you will be able of running it at 2000Mhz if you have corsair dominator GT 2000Mhz.