Tom's Hardware checks out how much bandwidth PCI Express graphics really need in their new scaling analysis. Here's a snip:
PCI Express quickly became an important growth engine for the graphics industry, because it allowed ATI/AMD and Nvidia to deploy two and even four graphics cards into a computer. And PCI Express will remain important for additional high-bandwidth upgrades, such as physics accelerators for 3D applications and games. The additional calculation power of extra graphics cards can be used to maintain performance at increased resolutions, to add visual features, or to improve performance at common settings. This last option is not that appealing, as many of today's graphics cards are powerful enough for typical resolutions of 1024x768 and 1280x1024. The growth potential is tremendous, thanks to ATI Crossfire and Nvidia SLI dual and quad graphics, because both solutions require the user to purchase a suitable platform to support the respective standards. An all-rounder - a motherboard that supports both Crossfire and SLI - does not exist, at least not yet.