GameMode is a daemon/lib combo for Linux that allows games to request a set of optimizations be temporarily applied to the host OS and/or a game process. GameMode was designed primarily as a stop-gap solution to problems with the Intel and AMD CPU power save or on-demand governors but is now host to a range of optimization features and configurations.
Nvidia GPU Rom editor that when paired with a nvidia rom flashing utility, such as nvflash, allows you to modify the bios contents to allow OS-independent overclocking, underclocking, unlocking restricted features, etc.