I saw this review of 2 different 64 GB RAM upgrades for the nMP. It includes benchmarks, so I thought it might be of interest to those frequenting this forum.
http://www.tekrevue.com/2013-mac-pro-ram-upgrade/
I believe this is the Hynix RAM they used. It is in my nMP right now and working great. Cheapest I've found by far.
http://www.superbiiz.com/detail.php?name=D3-18R16GH#
Using the same one, decided to go with 48gb (3x16gb of DDR3-1866) since it's fastest if you don't need the full 64gb.
Only problem with that is that you can't go to 64GB if you want late without buying 4 new sticks. It is recommended that all the 16GB sticks come from the same lot. Just an fyi if you were not await of that.
You don't need to worry about that if the modules have the same specifications. As long as they have the same voltage and are of the same type (unbuffered/registered) they are likely to work together, although generally the more difference they have the less-optimal performance will be.
RAM kits using only identical DIMMs from the same vendor's production run only starts to matter when you are overclocking memory. It should not be an issue at all with workstations, thats why we have specifications.
I'm looking at only going to 32GB of RAM for my nMac Pro when it arrives. That Hynix RAM seems like a great deal. I'm just wondering what would be better performance wise. 4x8GB or 2x16GB? There is mention of possibly taking a performance hit if I went with 2x16GB now and added another 2x 16GB in the future. Is that a huge worry? I'm leaning towards the 2x 16GB.
Thanks!
Go with the 2x 16GiB.
The Xeon E5-xxxx v2 CPUs have huge L3 caches. Most apps mostly fit in the caches, and don't see significant performance hits even with a single DIMM configuration.
If you want to look at some data that supports this opinion, read https://forums.macrumors.com/threads/1704700/ start to finish.
If money were not a consideration, go with the 4x8 and throw them away when you upgrade. For me - I buy systems with 24 DIMM slots and always buy DIMMs in multiples of 8 to populate all channels.
Thanks for the link! Very informative. I think I'll go with the 4x8GB as I'm just a hobbyist that doesn't really need 64GB, I just wanted to be more future-proof by leaving two slots open. The difference in the multicore score with 2 banks filled vs 4 banks tips the scales for me. I'm planning on selling this machine in 2.5 years before Apple Care gives out anyway.