Currently Being ModeratedAug 4, 2011 10:19 AM (in response to Zach Whittaker)
You probably should have 2 x 8GB
They don't mix with other size DIMMs
3-4 x 4GB = 12 to 16GB which may or may not suffice
Currently Being ModeratedAug 4, 2011 10:30 AM (in response to Zach Whittaker)
The optimum configuration in this computer is 3 chips of same kind. You can use (3) 2 Gb chips, or you can do like I did (3) 4 Gb chips. More ram doesn't hurt considering 64 bit OSes and 64 bit software utilizing more ram (or multiple 32 bit programs open). Also, I selected the DDR3 1333 ram. It's usually the same price and future proofs you in case you upgrade your processor at some point (not that I'm encouraging that, but it is possible). It'll run at 1066 Mhz with this processor, but with a processor that runs ram at 1333 Mhz, you'll be set. Hope this helps.
Currently Being ModeratedAug 4, 2011 5:43 PM (in response to Zach Whittaker)
I am somewhat confused that a system with 4 slots works best with 3 identical DIMMs.
Thanks for the answers. I'll get either 2 8gb DIMMs or 3 4gb DIMMs. Can I still use one of my old 1 gb DIMMs with the 3 4s option?
Is two 8s better or worse than 3 4s? 3 4s and a 1?
Currently Being ModeratedAug 4, 2011 6:57 PM (in response to Zach Whittaker)
It's because the architecture is referred to as "triple channel memory". So perfomance is optimum when only 3 slots are being used. On the other hand, generally you won't notice the difference with ath 4th slot being used.
Currently Being ModeratedAug 5, 2011 6:43 AM (in response to Zach Whittaker)
OWC has "special note" as does Crucial - no you can't mix.
MPG shows 8GB dimms have 15% better bandwidth
NO you don't need three 8GB DIMMs, you can go with two.
Currently Being ModeratedAug 6, 2011 8:14 AM (in response to The hatter)
From what I understood, you can't mix anything with the 8gb DIMMs. But the 4gb ones, it doesn't say anything about. I assumed I could keep one of my old 1gbs around to make 13, if I went that direction? Is that not correct?
I'm having trouble deciding. Two 8s would cost a lot more than three 4s, and I'm not sure I'll ever need more than 12 (or 13) gb for the life of this computer.
Probably end up flipping a coin or something..
Currently Being ModeratedAug 6, 2011 9:14 AM (in response to Zach Whittaker)
Yes, you can. Check out this thread from some one who has done something simliar with your machine and ram.
Currently Being ModeratedAug 6, 2011 9:39 AM (in response to AppleandtheMan)
Just to add a bit more clarity in terms of why it's optimum to use the triple channel more, or 3 of the same dimms in the first 3 slots, see below,
You may have noticed that Apple only populates the first three DIMM slots for each processor, even though there are four available memory slots per processor. This ensures the best memory performance. Each processor in the Mac Pro has three memory channels. Slots 1 and 2 are each connected to their own memory channel; slots 3 and 4 share the remaining memory channel. If slots 3 and 4 are both populated with RAM, the third memory channel must service both slots, thus reducing its memory bandwidth.
For best performance, try to populate only the first 3 DIMM slots.
Currently Being ModeratedAug 6, 2011 9:42 AM (in response to Zach Whittaker)
4 DIMM slots, 3 x 4GB
I don't see 1GB making enough improvement to warry keeping it.
OWC rebate isn't that much on Apple OEM RAM but they do buy back.
2 x 8GB does have benefit and leave you open to more later if needed.
Graphics means more can be done and cached into memory.
Yes 1-2-4GB DIMMs can be kept together.
4 x 2GB for the lightest uses.
Memory prices have been sliding down, they peaked a year ago.
No idea if you have pageouts, what apps, intended uses, or what you expect or will accept, but I always wait and then don't go down the penny-wise but pound-foolish road and having to redo.
No way to know though what future pricing will be.
I think MPG has enough about Mac Pro and memory.
Currently Being ModeratedAug 8, 2011 6:54 PM (in response to The hatter)
I'll buy 2 8gb DIMMs, I think. Thanks everyone. Also, the "two helpful answers" limit should be more clearly stated somewhere.
Last question, just for clarification- In my model machine, I can use 1333 MHz RAM. It will function absolutely properly at 1066 MHz, but won't run at 1333. True?
Currently Being ModeratedAug 8, 2011 7:34 PM (in response to Zach Whittaker)
Yes it'll run at 1066 Mhz and not at 1333 Mhz. You also won't have any problems.