NVIDIA introduced temperature-based boost in its GTX TITAN and GTX 700 series graphics cards. GPU Boost was first introduced in Kepler based GTX 600 series GPUs but it was a power-based boost system which dynamically increased the GPU clock above its default frequency taking power consumption and voltage into consideration. The shift to temperature-based GPU Boost 2.0 takes GPU temperatures in to account as well as the power factor. A user on ChipHell Forums claims that GTX 600 series BIOS Flash enables GPU Boost 2.0 in GTX 680/670/660 graphics cards.
Source: Chiploco (English), Chiphell (Chinese)
GTX 680 scores a little less than 6k with its actual BIOS with GPU Boost 1.0. So its quite an improvement with this BIOS mod.