At Computex 2012, we were told that the Gigabyte GeForce GTX 680 Windforce 5X Super OC would be able to perform close to NVIDIA's dual-GPU GeForce GTX 690, and could even beat it in certain benchmarks. Unfortunately, this turned out not to be the case, as you can see below from our 3DMark 11 benchmark, with the GTX 690 outperforming the Gigabyte GTX 680 by as much as 33%. Presumably, this boast was more likely due to an over-enthusiastic product marketer rather than any extensive internal testing. As such we have removed the GTX 690 from comparisons beyond the initial 3DMark11 benchmark. If you want a GTX 690 level of performance, you'll still need two GPUs.
Compared to our other GTX 680s, as expected, the Gigabyte Super OC was able to outperform its competitors on every benchmark. However, its lead was not as massive as one might expect, given its clock speeds and 'Super OC' designation, and it only beat our next best competitor, the Palit GTX 680 JetStream OC by about 2-4% on average. While the difference is small, this is about the expected norm. Against the reference design, it was about 15% better in general. This advantage is the reason you'll be paying a premium out of the box.
Part of the reason for Gigabyte's slightly subpar score may be due to its underwhelming GPU Boost performance. Our other custom cards, as well as NVIDIA's reference card, average a peak of about 100MHz extra core clock speed due to GPU Boost. On the other hand, Gigabyte's GPU Boost capped out at 1215MHz, which is only 78MHz above its default clock speed. This may be due to the high power draw required by the card's custom cooler, which would then reduce the excess power available to be utilized by GPU Boost.