First let’s see how the Nvidia GeForce GTX 680 2GB compares with the GeForce GTX 580 3GB, the fastest single-GPU card of the previous generation, the latter serving as a baseline in the diagrams:
So, the GeForce GTX 680 is an average 30-31% faster than its predecessor in 1920x1080 and 29-37% faster in 2560x1600. Recalling our comparison of the Radeon HD 7970 against its own predecessor HD 6970 in the same tests, we can see that AMD delivered a higher performance growth, but the GeForce GTX 580 was faster than the Radeon HD 6970. Besides that, the 256-bit memory bus of the GeForce GTX 680 should be blamed once again. It is obviously too narrow as is indicated by the difference in performance growth between the FSAA on and off modes.
Next goes a very interesting pair of summary diagrams that compare the Nvidia GeForce GTX 680 with the AMD Radeon HD 7970, both working at their default clock rates. The AMD Radeon HD 7970 serves as the baseline here.
Thus, the GeForce GTX 680 wins in all of our three synthetic benchmarks as well as in the following games: Just Cause 2, Lost Planet 2, StarCraft II: Wings of Liberty, Tom Clancy's H.A.W.X.2, DiRT 3, Hard Reset, Batman: Arkham City and Battlefield 3. The AMD Radeon HD 7970, on its part, is ahead of its opponent in Left 4 Dead 2: The Sacrifice, Metro 2033: The Last Refuge, Aliens vs. Predator (2010), Sid Meier's Civilization V and Crysis 2. The two cards are more or less similar to each other in S.T.A.L.K.E.R.: Call of Pripyat and Total War: Shogun 2.
If we take average numbers (that’s not quite correct, for example due to the StarCraft II: Wings of Liberty results), the GeForce GTX 680 is 9-16% ahead of the Radeon HD 7970 in 1920x1080 and 4-10% ahead in 2560x1600.
Comparing the results of the overclocked cards in the diagrams below, you should keep it in mind that our AMD Radeon HD 7970 was overclocked by 24.3/27.3% (GPU/memory) whereas the GeForce GTX 680, by 17.3/18.6% (without dynamic overclocking). That’s why the AMD card looks better in comparison with its opponents than at the default clock rates.
The GeForce GTX 680 2GB overclocked to 1186/7128 MHz is an average 4-11% ahead of the AMD Radeon HD 7970 3GB (overclocked to 1150/7000 MHz) in 1920x1080 and 1-9% ahead in 2560x1600.
And finally we can compare the performance boost each card gets from overclocking. It’s clear the AMD Radeon HD 7970 benefits more from overclocking in nearly every test both in 1920x1080…
…and in 2560x1600:
So, the clock rates of our GeForce GTX 680 grew by 17.3/18.6% and its performance increased by an average 12.8-16.8% in 1920x1080 and by 16.6-20.4% in 2560x1600. As for the Radeon HD 7970, the increase in its clock rates by 24.3/27.3% helped improve its performance by 18.2-22.7% in 1920x1080 and by 20.5-22.9% in 2560х1600.