In a preview of the next generation of GPU technology, ATI showed their Crossfire technology at the Computex show in Taiwan this week. CrossFire ties two graphics cards together, on an approved PCI Express motherboard with three ways of balancing the load between the two cards. The load can be shared by splitting the screen, rendering alternate frames on each card or using a Supertiling mode.
CrossFire is moderately restrictive and definitely "next generation". It requires an approved Radeon Xpress 200 CrossFire-based motherboard using the PCI-Express architecture. The PCI Express architecture puts Graphics cards on the same high speed bus as memory, processor and Input/Output. This means that more than one graphics card can exist on the same system.
With an approved CrossFire motherboard and CrossFire Graphics card, any Radeon X800 PCI Express series card can be used in the configuration – the second card does not have to be a CrossFire card.
Even though the CrossFire architecture requires a PCI Express motherboard, most of the graphics compositing is done with direct connections using a DVI/DMS combination cable. This is similar to the approach taken by NVIDIA with their "Double Graphics Processing", which also relies on a PCI Motherboard (SLI-capable in this case) and two identical NVIDIA GeForce 6800 Ultra, 6800 GT, or 6600 GT cards linked together.