TweakTown checks out the performance of NVIDIA's NF200 bridge chip on Intel's P67 platform, you can check out the results over here.
Unlike most performance motherboards that by default carry only an x8 / x8 setup when SLI or CrossFire X is used, the ASUS Maximus IV Extreme offers us the NF200 chip to add more PCI-E lanes to the board. Over the last few years we've seen companies implement the chip to boards to help move the default SLI or CrossFire X setup from x8 / x8 which is offered via the Intel chipset, to x16 / x16 via the NF200 chip.
When you move away from a two card setup and into a three card one, boards without the NF200 chip would run x8 / x8 / x4, while with the NF200 we're able to achieve x16 / x8 / x8 which when having so much power on hand, is extremely appreciated. ASUS do it a little differently, though, and they do it in a way that has confused people. On the Maximus IV Extreme and Extreme-Z, their P67 and Z68 boards, by default they offer x8 / x8 via the Intel chipset. It isn't until you add a third card into the mix that the NF200 chip comes in handy, because in that situation we get a x8 / x16 / x16 setup."