For overclocking the GeForce GTX 1080 Founders Edition we used a pre-release version of Evga's PrecisionX. The software allowed us to increase the base clock frequency from 1607MHz to 1827MHz, though thanks to Boost technology the frequency almost never dropped below 2GHz when gaming, often hovering around 2054MHz.
The GDDR5X memory was also very willing to go faster reaching 5858MHz, a 17% increase over the stock frequency.
The overclock allowed for a rather large 17% performance boost in F1 2015 at 4K, taking the average frame rate to 90fps. This means that the GTX 1080 becomes a whopping 45% faster than the Titan X and 64% faster than the Fury X.
This time we find an additional 16% more performance at 4K, allowing the GTX 1080 to break the 60fps barrier in DOOM at 4K.
Finally, we enjoyed a more pedestrian 11% performance bump in The Witcher 3. While not as impressive as the first two titles, this extra performance is very much welcomed given the already lowish frame rates when maxing out the visuals at this resolution.