Why a 6-core system can hold less memory than a 12-core system?


macrumors 603
Original poster
Jul 23, 2007
Hello, considering to buy a 3.33GHz 6-core MacPro or a 3.06GHz 12-core one.
How come the 6-core system can hold only 32GB while a 12-core one can hold up to 64GB? Is the motherboard difference? If I buy a single cpu machine now, can I upgrade to a dual cpu system? Thanks.


macrumors 603
Original poster
Jul 23, 2007
Did you even look at Apple's marketing pages?


I'm sure there is a user manual you could dig up if gave it even half a try too.
Why the dual cpu system has twice more slots? Two years ago, I read that a single cpu system could be upgraded to a dual cpu system. It just costed more and it was difficult to find a compatible cpu. So, it means that the motherboards on the two-year-old systems were the same. Do you mean the latest MacPro systems have different motherboards?


macrumors 601
Jul 17, 2010
No same MoBo they have different daughter cards. You can get a duel socket DC for a ton of cash at OWC.


macrumors 6502a
Oct 28, 2008
If you look at the 2006 and 2008 models then they had the same single board that had 2 sockets installed on. From 2009 onwards then the CPU's sit on a separate daughter board that also contains the memory slots on the daughter card.

To upgrade then you have to acquire the necessary daughter board and processors / heatsinks etc, from the places that sell spares for the Mac Pro's.

Also note that the single socket versions use the 3500/3600 series of Xeons which are not Dual CPU system compatible so you would not be able to reuse the existing CPU from the existing daughtercard.


macrumors newbie
Aug 4, 2012
You can actually put in 96GB in the 12-core. Same with the 2009 Nehalem. The Quad goes up to 48GB (3x16GB) and the 8-core goes up to 96GB (6x16GB). They have lab tested these combos to be stable.

There is the certain amount of memory per processor.