A worker at microsoft build a gaming pc with 3x 7970 and tried playing dirt 3 on it. In the end (with some help of custom made drivers by AMD) they got it to work on high settings with an average fps of 60.
Pointless as it is, it is awesome they tried it
Stupid thing tho, they are using a 750 watt psu. And it boots fine and you can play for a while but than it shuts down due to not having enough power. Why on earth didnt they get a proper psu.... -.-