I'm looking at getting 2 of the gtx 670 windforce cards
I noticed that the Extreme board has a pci-e x16 slot for both of the cards while the Formula board only have one x16 slot and the other card would be forced into the x8 slot. How will this affect my FPS and benchmarks and what hardware was used in the 2012 GPU charts that were done here at Tom's Hardware?
More aboutmaximus extreme formula
PCIe 3.0 x8=PCIe 2.0 x16 and is still enough for high-end cards like the 670. I wouldn't worry about it. TechPowerUp already did a review on PCIe scaling.
yeah, 8x at pcie3 still has plenty of bandwidth.. as said above, its like having a 16x pcie 2 slot. just make sure you pair it with the appropriate cpu, an ivy bridge i5 or better. the sandy bridge cpu's have only pcie 2 controllers.
Even PCIe 2.0 x8 is still enough for a 670. Sandy Bridge or Ivy Bridge really doesn't matter but I'm sure you recommended IB so that OP can get PCIe 3.0 functionality.