Computers are a cutthroat business, and often times compatibility has nothing to do with the technology at hand, but licensing agreements and corporate politics. All that stands between SLI on an Intel motherboard (or CrossFireX on Nvidia silicon) are drivers and a BIOS tweak. Don't believe it? Look at HP's Blackbird 002.
Now take that same concept and apply it to the heated GPU wars. With AMD gobbling up Havok and Nvidia acquiring AGEIA, the race is on to not only deliver the fastest graphics card, but physics acceleration too. Of course, developers would prefer one standard, and Nvidia indicated it would make PhysX available for free through its CUDA SDK, but if ATI had any plans of going that route, it appears they've been beaten to the punch.
To learn more about the modified drivers and where and when you can get them, click through the jump.