Here is a table with the full test results.
The first pair of summary diagrams compares the AMD Radeon HD 7970 GHz Edition (at 1050/6000 MHz) with the ordinary Radeon HD 7970 (925/5500 MHz):
The 13.5% higher GPU clock rate and 9.1% higher memory clock rate make the Radeon HD 7970 GHz Edition faster by 9.3 to 9.6% at 1920x1080 and by 9.9 to 10% at 2560x1440. The largest advantage can be observed in Aliens vs. Predator (2010) and Lost Planet 2. The advantage of the GHz Edition card is the smallest in Metro 2033: The Last Refuge.
Now let’s see the AMD Radeon HD 7970 GHz Edition 3GB compete against the GeForce GTX 680 2GB at their default clock rates:
The GeForce GTX 680 is still faster in the semi-synthetic benchmarks, in Lost Planet 2 and (at certain settings) in Just Cause 2, Hard Reset, Batman: Arkham City and Battlefield 3. The new AMD Radeon HD 7970 GHz Edition wins the rest of the tests, enjoying a large advantage in such games as Aliens vs. Predator (2010), Sid Meier's Civilization V, Total War: Shogun 2, DiRT Showdown and Sniper Elite V2. Well, we shouldn’t forget that the performance of a graphics card depends on the particular game and its rendering engine. For example, the GeForce GTX 680 would be faster in StarCraft II: Wings of Liberty and Tom Clancy's H.A.W.X. 2 but we’ve excluded these games from our list because the former is too CPU-dependent and the latter, too old.
And finally, let’s compare the AMD Radeon HD 7970 GHz Edition overclocked to 1250/6680 MHz with the ASUS GeForce GTX 680 TOP overclocked to 1217/7168 MHz:
The picture is overall the same, yet the GeForce GTX 680 has improved its position somewhat thanks to better overclocking (in percentage).
It wouldn’t be correct to claim that the AMD Radeon HD 7970 GHz Edition is the fastest single-GPU graphics card available today because our tests do not show it to be overwhelmingly better than the reference GeForce GTX 680. However, the increased clock rates make the new card 10% faster than the previous top-end solution from AMD, which really makes a difference in some games.
Besides, the release of the GHz Edition graphics accelerator ended up being not as exciting as we would expect it to be, just because there are currently a dozen or more Radeon HD 7970s cards with overclocked frequencies available in the market right now, some of which even have higher clock rates than the reference GHz Edition. That’s why the new card cannot really surprise us with its performance. Overclockers might have expected it to bring about a new stepping of the Tahiti XT chip with lower voltage and higher overclocking potential, but we couldn’t find any of that during our experiments. Hopefully, off-the-shelf samples of the new card will be more overclocker-friendly.