Hi I'm sorry if this thread already exists but I could not find it. In the new 8-core Mac Pro is it better to have 6gb or 8gb of RAM. Money is no option I just want to know which one will run the fastest since the Mac Pro uses tri-channel memory.
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New Mac Pro 6gb or 8gb of RAM
- Thread starter bumzo1
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More RAM is always better depending no what applications you are using. I currently have 8GB of RAM in my MP. Im planning on upgrading to 12 or 14GB here very soon. 
6GB will enable tri-channel mode which will speed things up for certain applications. Another alternative is to go for 8gb and then get another 2x2GB chips from Crucial. Its cheaper to buy 8GB from Apple and 4GB from Crucial than it is to start off with 6GB and get 12GB from Crucial to replace it. If money were no reasonable issue then that'd be the best route imo. Of course, 6GB would be more than enough anyway so its up to you.
As far as applications... where does Photoshop stand? I am going to make a purchase within the next month here and cannot decide on a RAM configuration.
Depends what you do in Photoshop. 6GB of RAM is really quite a lot for most people these days. I mention the 12GB option since it offers triple channel memory speeds but is also very future proofed. The idea of having to chuck 6GB of RAM to upgrade to 12GB at a later date would be quite off putting I'd think.
So now I am a little confused on the 8-core vs. 4-core. Is it that much a difference when considering memory speed? That kind of scared me into getting an 8-core now.
Yeah, 6 or 12 but not 8. More is NOT always better.
I've never seen a good explanation on why Apple didn't have multiples of 3 rather than the 4 or 8 memory slots.
It depends what you're doing. Some things will run much better with faster memory bandwidth.
Yes, you have to actually test the memory bandwidth. I've checked my machine several times with different configurations and on my 06 Mac 1,1 and 4 and 8 DIMMs are about 12% to 15% faster than 2 or 6 DIMMs on average.
12gb if it is an octo core
It seems the sweet spot is 6 dimms on the octo core machines. 2gb dimms are very cheap right now, and basically they are double sided versions of the 1gb sticks. In fact, the ones I purchased from OWC are exactly the same as the stock Nanya dimms but double sided instead of single (2gb instead of 1gb). Machine runs great. 4gb dimms are just too expensive right now.
Noushy
It seems the sweet spot is 6 dimms on the octo core machines. 2gb dimms are very cheap right now, and basically they are double sided versions of the 1gb sticks. In fact, the ones I purchased from OWC are exactly the same as the stock Nanya dimms but double sided instead of single (2gb instead of 1gb). Machine runs great. 4gb dimms are just too expensive right now.
Noushy
Aha, that answers a question I've had. From what I understood, if you had six dimms, four of which were matching an in the right bays then those four would run in dual channel mode leaving the other pair in single. Does it actually bring all of them down to single mode? I've got 4x512MB and 2x1GB at the moment and I've been worrying about my memory bandwidth ever since I discovered my code was running faster on my Unibody 2.53GHz MacBook Pro with 4GB DDR3 memory than it was on my 2.66GHz Mac Pro overclocked to 2.8GHz with FB-DIMM 667MHz memory. As in, it was running about 50% faster.
From what my tests show the first 4 DIMMS (sizeof smallest pair) will get the dual channel bandwidth increase. I dunno how double-sided single-sided affects this and I don't remember what mine are now in order to guess or retest.
From what my tests show the first 4 DIMMS (sizeof smallest pair) will get the dual channel bandwidth increase. I dunno how double-sided single-sided affects this and I don't remember what mine are now in order to guess or retest.
Hmmm.... I guess I should bite the bullet and get another 2GB so that its all matching pairs. I bought some 800MHz FB-DIMMs a few weeks ago for an absolute steal hoping that they would be backwards compatible (they were from an 800MHz XServe). Alas, no.