Crossfire was not thinking about until AMD released Catalyst 13.8 Beta in August 2013. With this driver is Battlefield 3 is finally playable with two cards.
Have had more problems with my 7970 (both Crossfire and when I only had one) than I would expect for 6500 SEK, so unfortunately I have to deduct stars for it.
Playing in 2560x1440 @ 110 Hz. Most likely, the DVI cable that can not handle higher bandwidth, so I can not guarantee that the card can handle 120 Hz at that resolution.