Originally Posted by Domino
theoretically speaking, if I were folding on a server board with 2 6 series 8 core opterons and 3 gpu clients... how much ram I'd actually needed. and.. say.. if I needed 8 gb of memory, would 4 Gb of high performance memory be best? or if 16gb is good, would 8gb of high performance memory be best? for example ... comparing 16 Gibbs of 1333 at cl8 as opposed to 8gb at 2000+ (if the g34 chipsets even support that type of memory)
Basically Magny-Cours G34 (61xx) will run at 1333, Interlagos and Abu Dhabi (62xx and 63xx) support up to 1600.
In some special cases (4P Supermicro mobo, special BIOS and special memory), MC can run at different speed and tighter latencies. But that is a special case, as said. You can start by reading here: http://www.overclock.net/t/1212613/guide-building-a-2p-4p-from-start-to-finish-along-with-ppd-benchmarks-gallery/
About the amount, the more threads you have folding=the more memory will be used. I have 48 cores folding BA right now, 32 GB total memory, Fah-core takes about 7.5% of this (~2.5 GB). I run CLI Linux and have nothing else going on this machine so I have nearly 28.5 GB free too. Recommended amount per core is 500-1000MB though, iirc.
You wanna fill up AT LEAST 2 channels/CPU, I tried with single, dual, triple and quad channel on my machine and saw a huge jump between single and dual, while the gain going up to triple and quad was less noticeable it was still a gain.
2 GB sticks will suffice, and if you fill up all channels you'd have 16GB which will be plenty. The standard these day seem to be 4 GB sticks, then you will have 32GB which is more than plenty for anything folding related. Find something that will run at or below 1.5V though. I ran the Samsung Wonder ram for a bit on my machine, they may help eek out a little extra mileage (slightly lower power consumption due to lower operating voltage).