I am wanting to do a new build soon. I am really wanting to do an eyefinity setup. 7970s are dropping like crazy. I've seen them for 300 on ebay.
So i am thinking two of those in crossfire. The thing i'm wondering is if an i5 can handle those. I am willing to go AMD if the new 8350 is better suited for dual cards over an i5. I can't find any reviews on how the processors scale with sli / xfire.
I also have a corsair tx750 (not version 2) with 4 6pin +2pin PCIe connectors. Could this handle two cards and an i5/i7 O/C'd?
I am going to end up buying used more then likely, but the main question is if I need the extra i7 threads. If so it seems an 8350 might do better then the i5 for this setup at the price. However, for gaming in general amd is way behind any i series.
The advantage of the i7 over the i5 is Hyper Threading (HT) which more or less creates 4 virtual cores. HT can boost performance of programs that have been designed to use HT. How much of a boost? It depends on how well HT has been implemented into the design of the program. So generally speaking is can be 0% to maybe as high as 40% if the program was extremely well designed.
How much added performance will HT give to games? 0%. Games are not designed to use HT. In fact, over the past several years, benchmarks have show that on average HT reduces performance by 1% - 2 % in games. It's very small, but if do not use programs that can take advantage of HT, then there is no real point in buying an i7 CPU.
I have 2 7950s in Crossfire with an Eyefinity system and an i5-2500k and it's more than enough power to run everything. I am always limited by the GPUs at that resolution. So don't bother with the i7s anyways.
Toms hardware even suggests that the best CPU for any sort of money is the i5 3750k especially when you want to overclock. I am a big big fan of Amd but sadly the Fx processors can simply not deliver in performance compared to an Intel processor.I would say by a 3750k which is more than perfect and spend the extra money on getting a higher end 7970. I would also agree with you that buy two 7970 is the way to go because when overclocked they have very similiar perfomance to 680's and there you are basicallly get a setup that is as powerful as a gtx 690 for only 600 or so dollars . Seems like a great idea
Edit: Also the power requirements should be fine 750W is heaps you would only need more if you were doing some with three or more high end graphics cards