Crossfire vs sli
Getting 2 7870 to run in crossfire, or would i be better getting 2 660 in sli?
AMD seems to be having problems with frame time lag resulting in micro-stutter with 2 cards. Nvidia has this issue too, but far less intense. For that reason alone, I would opt for the Nvidia cards.
There is absolutely no way that anyone should be seriously considering Crossfire at this time. The latest test methods that use FCAT to examine frame latency have uncovered a very serious problem with Crossfire. Basically they have found that adding a second AMD video card is a waste of money. On the other hand, they have found that Nvidia's frame smoothing technology works very well and delivers near perfect scaling for a pair of cards in SLI.
"AMD CrossFire configurations have a tendency to produce a lot of runt frames, and in many cases nearly perfectly in an alternating pattern. Not only does this mean that frame time variance will be high, but it also tells me that the value of performance gained by of adding a second GPU is completely useless in this case. Obviously the story would become then, “In Battlefield 3, does it even make sense to use a CrossFire configuration?” My answer based on the below graph would be no."
"In half of our tested games, the pair of Radeon HD 7970s in CrossFire showed no appreciable measured or observed increase in performance compared to a single HD 7970. I cannot overstate that point more precisely: our results showed that in Battlefield 3, Crysis 3 and Sleeping Dogs, adding in another $400+ Radeon HD 7970 did nothing to improve your gaming experience, and in some cases made it worse by introducing frame time variances that lead to stutter."