If im running three GPU cards in sli, one Physix card, and a PCI-E SSD... would you reccomend a sandy bridge extreme (LGA2011) or other? Im afraid of losingperformance from not having enough PCI lanes/bandwidth.
note: im getting CPU for free up to $1000... so the i7-3970x will cost me about 50 bucks total after tax.
You won't even need the PhysX card with 3 GPU's in SLI, anyway. You wouldn't even need a dedicated PhysX card, period, but absolutely not with 3 cards in SLI. It would just sit there doing absolutely nothing.
Just forget about the PhysX card. That takes us to 4 PCIe cards.
With that said, because of the PCIe SSD (still a lot of bandwidth needed because of the 3 GPU's hogging a major chunk of it), I think X79 is the way to go, yes.
I think it's overall a huge waste, but if you can get a 3970x (are you sure it's not a 3960x?) for free basically, it doesn't even really matter.
Even it is a 3970x (which was just announced, apparently), there's no need for it. A 3960x is basically the same CPU, just clocked 200Mhz lower (which you can easily OC the 3960x to make up for it).
Actually, I only have 2 card sli and a physix card planned atm, just wanted to leave options open for a third in the future. Im gaming at 2560x1440, and no one tests sli with dedicated physix at higher than 1080p. Until I see data for tri w/physix at that resolution im going to keep it in mind.
Also, Ive been building off a two year old PC and slowly adding hardware - including a third radiator. The name of the build is overkill (and overpriced). All GPUs and CPU will be on same loop (2 pumps), with a 1x140 rad, 2x140 rad, and 4x120 rad - so I shouldnt have any problems with the extra heat from i7-3970x.
Im teaching myself about price/performace from first hand experience, and im having fun doing it.. even though it kinda hurts the wallet ><