Some of you may have noticed that from one website to another the performance of the GTX 670/680 isn't the same. It's mainly due to the GPU Boost. Wazzat? The GPU Boost has been first introduced by nVidia for the GTX 6xx series and acts like the well know Turbo clock on Intel and AMD processors. For example: the graphics processing unit of the graphics card see it's clock raising for a while until it reaches the TDP limit.