With the in-development Linux 4.4 kernel, NVIDIA GeForce GTX 600/700 series (Kepler) graphics cards are manually re-clocking a lot better to allow better performance on this unofficial NVIDIA Linux driver.
The Nouveau Linux 4.4 pull request enables re-clocking support for GDDR3-based graphics cards from the G94 through G200. However, for modern NVIDIA customers, the GDDR5 PLL stability fix and other Kepler changes is leading to a much better experience. See Experimental Nouveau DRM Branch Yields Better GDDR5 Kepler Re-Clocking. In my testing so far of the post-4.4-rc1 code, the Kepler re-clocking with graphics cards using GDDR5 video memory is indeed working much better!