Guys here's an interesting article on gpu performance on the now popular p67 platform. It seems nvidia has an advantage here in terms of scaling as amd seems to be having a performance hit in x16 ,x8 & x4 modes.
^^ They are using single gpu across all modes to check the performance hit in different bandwidths provided. Amd cards are taking a performance hit in p67 platform.
The link asingh provided reviews the multigpu performance(both sli and cf) on the three platforms. It seems again like nf200+p67 is the best platform currently for multigpu setup.
Adding nf200 enables triple gpu setup in p67 in form of x16-x8-x8 mode. So thats really good.
Check their conclusion:
Even though our attempts to make both platforms equal gives LGA 1366 an even greater bandwidth advantage, LGA 1155 still wins. Were we to remove the artificially-low O/C limit imposed upon our P67 platforms and run them at the 4.4 or 4.5 GHz we know they'll take, it would simply win by an even greater margin. And if that reasoning isn’t enough to negate the newer platform’s PCIe limits in the eyes of extreme gaming enthusiasts, adding Nvidia’s NF200 to LGA 1155 enables X58-style x16-x8-x8 connections.
While the NF200 doesn’t completely solve the dearth of PCIe lanes available on LGA 1155 platforms, its ability to send identical data to multiple cards makes it perfect for SLI and CrossFire. That benefit, when combined with the Sandy Bridge processor’s superior performance and overclocking capabilities, slams the lid on the coffin for X58 gaming. Anyone who needs the added flexibility of X58 to host other devices, such as high-end drive controllers or six-core processors in a workstation environment, must bow to the gaming superiority of NF200-equiped Sandy Bridge motherboards like Asus' P8P67 WS Revolution.