eidt: the 6 core is on a workstation board it appears and not a server board. The server boards may or may not be dual channel capable but the 4 slot boards are 3 + 1, so disregard the rest of this post. Sorry about the misinfo. If only Apple had spelled this out for us. . . . . I spoke with the Micron engineer who personally tested the 4, 6 and 12 core 2010 mac pros on August 9th with regard to memory compatibility. After a long conversation and some additional research he confirmed that in fact the six core Westmere Mac Pro is a dual channel memory system (integrated in the chipset) and NOT a triple channel system like the 2009 Nehalem chipset Mac Pro systems were. Therefore the best way to populate the 4 slots is to populate them all with identical memory which will run in effect in dual channel mode. In addition. He stated that he in fact tested 8GB sticks of 1333 ram in the six core system and it did recognize and run the 8GB sticks. In fact Crucial has these 8GB sticks (albeit very expensive) listed now on their site as compatible with the 2010 Mac Pros. I certainly wish I had this info when I placed my memory order with Transintl. Nevertheless, it seems to indicate that the max amount of ram for the six core is looking much better indeed. By the way, the board is a derivative of the Intel 5520 for anyone who is interested. "Unlike Core i7, however, mainstream desktop/mobile Westmere chips will not feature a QPI bus or a triple-channel memory controller. Rather, we'll revert to a dual-channel controller and have no QPI clock to worry about"