8) Thanks to the PCI Express (PCIe) interface, combining two graphics cards in an SLI configuration is easily achieved. Just plug two identical GeForce 6 or GeForce 7 cards into the motherboard, and connect them with the SLI bridge connector. The two cards will then split the 3D rendering load between them, which can result in a performance improvement of up to 70 percent in everyday life. Now that PCI Express motherboards are available with PCIe x32 - or, more correctly, two x16 slots - there are also some new and intriguing possibilities.
For more :
http://www.tomshardware.com/2005/12/...uad_gpu_setup/
Two's Company, Four's a WOW! Sneak Preview of NVIDIA Quad GP
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