The Tech Lounge posted a news story on ATI's Crossfire Xpress 6400 Platform

After recent news of NVIDIA launching their 4xSLI platform, ATI now announced the launch of the Crossfire Xpress 6400. With an Xpress 6400 motherboard you will be able to purchase two master cards and two slave cards from the X1000 series to power a single display with FOUR video cards. While this may not exactly be the making of a mainstream computer system, you can bet green team isn't happy about it.

ATI Launches Crossfire Xpress 6400 Platform