The dual GPU GeForce 9800 GX2 card requires at least x8 PCI Express 2.0 to deliver high frame rates. Going to x4 link mode clearly bottlenecks the graphics flagship.
Crysis shows a noticeable impact when running on a reduced number of PCI Express 2.0 lanes, but only at very high quality. It’s amazing to see that you’ll get almost full performance even at x4 link mode.
These results confirm what we already saw on the ATI Radeon HD3850 card: Flight Simulator X heavily depends on PCI Express bandwidth. Reducing the x16 PCI Express 2.0 links to slower ones noticeably bottlenecks the simulator, as access to textures stored in the system main memory becomes far too slow.