nMP ram configuration banks

fabric17

macrumors newbie
Original poster
Aug 3, 2011
23
1
I have a question about ram size modules:

is possible to have something like (4GB + 8GB) + (4GB +8GB) ?
or even (4GB + 4GB) + (4GB + 8GB) ?

I have not tested :-(
now I have a factory : 4 + 4 + 4
And I want to ask if: the bios is refusing the configuration ? or is only a performance issue?


I have found out this:

MacPro firmware prefers not mixing 8GB with other modules
http://macramdirect.com/macpro.html

thanks

f.c.
 
Last edited:

CH12671

macrumors 6502
Dec 29, 2013
350
0
Southern US
It has been discussed a few times. Here for example. Have you tried it? I can't quite understand if you are saying you tried it and it didn't work, or are you asking if the bios will refuse/vs just a performance hit?

Unless someone else tries it and it doesn't work, I plan to go 2x8 and 2x4 on mine for a while, and eventually 4x8. I will probably do benchmarks with different configurations (i.e. just the stock 3x4, then the 2x8 by itself, then the 2x8 + 2x4, and then even as 4/8 + 4/8). But it will be March before mine ships.
 

CH12671

macrumors 6502
Dec 29, 2013
350
0
Southern US
Flex is not enabled on the xeon processors that come in the nMP. But there is some question as to whether or not that even matters in a quad channel machine.

Definitely you can't mix and match 16 GB chips with 8's or 4's because the 16's are RDIMM's, and the others are unbuffered. Other than that, we just need someone to try it. If no one tries it before April, then I will. Worst case scenario I pull all 3 4's out and have 16 to start...then add 16 more in a month or two....
 

fabric17

macrumors newbie
Original poster
Aug 3, 2011
23
1
Thanks

Really helpful!
I will try (and test) the 4+4 + 4+8 configuration to start (for a total of 20GB)
I bet that there will be a ram speed "small downgrade" but the total effect of upgrading will be positive

Take a look at the official support page. There are some recommendations there, but from what I read mixing the 4GB and 8GB UDIMMs should be possible.
 

CH12671

macrumors 6502
Dec 29, 2013
350
0
Southern US
Really helpful!
I will try (and test) the 4+4 + 4+8 configuration to start (for a total of 20GB)
I bet that there will be a ram speed "small downgrade" but the total effect of upgrading will be positive
Please post results. Benchmarks if possible! I agree, probably a performance hit, but still with overall gains!