Fast Sync: As of the 368.22 GeForce drivers, Nvidia has introduced a new form of VSync called Fast Sync. This VSync method is similar to Triple Buffering in that it uses three frame buffers. However, the behavior is slightly different: the GPU is not held back in any way by the display's refresh cycle. With Fast Sync enabled, the game engine will behave as though VSync is Off, hence the GPU can render as many frames as it possibly can at all times, which results in the highest performance, no framerate cap, and minimal input lag. Whenever the display needs to refresh, the GPU determines which latest available whole completed frame to send to the display, which in turn prevents tearing. Thus Fast Sync can provide the best aspects of both VSync Off and VSync On, without the negatives of either.
The major downside of Fast Sync is that (as a senior Nvidia engineer explains here) it is only truly beneficial in very high FPS situations, typically when your framerate is at least 2-3x your display's refresh rate (e.g. 120-180 FPS and above on a 60Hz monitor). At lower framerates, because of the way Fast Sync essentially samples/drops frames, you may notice similar sorts of latency issues as traditional VSync On, as well as stuttering. So in practical terms you should only consider enabling Fast Sync in older games, or newer games where the settings have been turned right down; basically only in games where you can guarantee very high framerates.
The Fast option is currently only available under the Vertical Sync setting in the Nvidia Control Panel for GTX 1080 and 1070 GPUs, but can also be enabled for the GTX 600 series and above using Nvidia Inspector as covered here.
There is no simple solution when it comes to VSync. Whether you enable it, disable it, use Adaptive VSync, or set an FPS limit, there are always some compromises involved. The only no-compromises solution is to purchase a G-Sync capable monitor, which is worth considering the next time you want to replace your display.
Comment