The diagram below compares two Radeon HD 7970s in CrossFireX mode with a single such card, the latter serving as a baseline.
The summary diagram makes it clear where CrossFireX technology works well and where the Catalyst driver and game-specific profiles need polishing off. The performance benefits are huge in such games as Just Cause 2, Aliens vs. Predator (2010), Sid Meier's Civilization V, Tom Clancy's H.A.W.X. 2, Total War: Shogun 2, Crysis 2, DiRT 3, in the AA mode of S.T.A.L.K.E.R.: Call of Pripyat, in Unigine Heaven and in the heavier modes of both versions of 3DMark.
On the other hand, CrossFireX is inefficient in Batman: Arkham City, Battlefield 3 and Hard Reset. You can see that such games are few and we can expect the situation to improve as the Catalyst driver gets optimized. We guess we will test this CrossFireX configuration once again in half a year to check this out.
You can view a table with detailed test results as well:
The XFX R7970 Double Dissipation Edition graphics card seems to have but one downside. Its accessories are too scanty for a top-end $550 product. Otherwise, we can hardly find any other issues, even though the high potential of the original cooler is not fully utilized. The cooler is anyway better and quieter than the reference one. The XFX R7970 Double Dissipation Edition overclocks like any other HD 7970 and delivers the same performance because it has the same PCB and clock rates as the reference HD 7970. So, it is a well-made product with an original cooler that costs about the same money as ordinary HD 7970s.
Running two Radeon HD 7970s in CrossFireX mode only makes sense at very high settings such as 2560x1600 with 8x or 4x antialiasing. If the game (or benchmark) supports CrossFireX correctly, you can double your frame rate and enjoy smoother graphics. The downside is that CrossFireX technology doesn't work correctly in each game. And even if it does, there can be problems with the bottom frame rate. Hopefully, this is only because the Tahiti processor is new, so its CrossFireX compatibility will improve in the near future.