Adaptive VSync is a feature NVIDIA is integrating into the GTX 680 launch that attempts to finally provide the perfect solution for gamers that don’t want stuttering and visual tearing in their gaming.
VSync (vertical sync) is a technology that has been around forever and limits the number of frames being rendered to match the refresh rate of the display (usually 60 Hz). While this does provide a gamer with tear-free gaming, it also means the frame rate has to "jump" between levels rather than smoothly transitioning between them. If your frame rate dips below 60 FPS then the card has to start outputting 30 FPS, the next multiple down from 60 Hz. If it dips even further you would jump to 20 FPS, etc.
The problem is that those jumps can appear in the game as stuttering and the difference between running a game at 30 FPS and 55 FPS is pretty dramatic.
With VSync disabled completely though, you will see visual tearing on horizontal lines in games. It is likely that every gamer has experienced this scenario.
NVIDIA’s Adaptive VSync technology actually disables VSync when the frame rate drops below the 60 FPS level so the game can smoothly transition to 58, 57, 45, etc frame rates without stuttering, and without dropping all the way to 30 Hz. This technology is possible because NVIDIA’s driver is able to tell how many frames it is rendering and recognize when the transition is about to happen, disabling the feature. You can enable this in the control panel in the same drop down box as you would normally find VSync options.
Obviously we wanted to see this at work for ourselves so I ran through some Metro 2033 with the GTX 680. You will see three collections of data: standard VSync Off, standard VSync On and Adaptive VSync.
With VSync off we averaged just over 63 FPS with a maximum frame rate of 107 FPS. With standard VSync enabled you’ll see the average fall all the way to 42 FPS but more importantly look at the red line in the top graph – the frame rate dips to the 30 Hz and back 60 Hz very quickly and when that happens you will often see a stutter as the transition takes place.
With Adaptive VSync enabled (the green line), the performance closely matches the VSync disabled line (blue) when under 60 FPS but caps there as expected with VSync technology, preventing tearing.