Overclocking the Founders Edition of the GTX 1070 wasn't overly successful as we were only able to push the base clock from 1506 MHz to 1726 MHz, which should put the boost clock at or above 1827 MHz, or only a 6% increase. However, the actual operating frequency was consistently above 2000 MHz so that is more like a 16% overclock.
Not as much time was spent tuning the GDDR5 memory, but we were able to test at a stable 2177 MHz, which admittedly isn't a huge boost over the stock 2000 MHz.
Our overclock enabled a 12% performance boost for the GTX 1070 at 1440p in Far Cry Primal, taking the average frame rate from 52 FPS to 58 FPS and leaving the GTX 1070 12% behind the stock 1080.
This time our overclock allowed for 13% more performance when testing Doom. The GTX 1070 went from 91 FPS on average to 103 FPS, just 6% slower than the GTX 1080.
Finally, we see an 11% gain from the overclock when testing with The Witcher 3, meaning the 1070 was just 9% slower than the 1080.