Here: http://www.pcper.com/article.php?aid=212
Back to the technology aspect of it all, we can see that ATI’s claims of bandwidth levels on the NF4 SLI X16 chipset are simply not valid. Our real world testing shown here obviously demonstrates that even with ATI’s cards involved to eliminate chipset/GPU tweaks, the secondary x16 PCIe slot has no noticeable performance deficit compared to the primary x16 PCIe slot.
Even more indicative of invalidity of ATI’s data is the fact that even when we desperately TRIED to make the NF4 X16 secondary GPU slot slower by bogging down the system with almost a full Gigabit of networking data, a maxed out SATA connection and a maxed out USB/Firewire connection, it didn’t work. The secondary GPU slot performed nearly the same as the primary slot with only very small performance differences under 3%.