What is adaptive sync and how does it affects the gaming experience? What is G-Sync / FreeSync and why would you need that?
A TFT monitor updates the screen at a fixed rate (known as refresh rate), which is usually something between 60 and 100Hz. The graphics card (GPU) renders new frames independently at a different rate. Depending on how demanding a game is, the number of frames per second (FPS) can vary a lot, from a few frames all the way up to several hundred frames. When a new frame is ready, it will be sent to the monitor. Now what happens if the monitor is just in the middle of a refresh cycle is that the upper half of the screen will display the previous (old) frame, whereas the lower part already shows the next (current) frame. This artifact is called screen tearing and can be very disturbing in some situations. The higher the refresh rate of the monitor, the less will it be visible. But even at e.g. 120Hz, tearing is still visible as a slight flicker.
There are several options available to eliminate this issue:
- enable vertical synchronization (VSync)
- enable FastSync
- use a monitor that supports an adaptive sync technology such as
FreeSync or G-Sync
VSync basically synchronizes the frame rate of the graphics card to the refresh rate of the monitor. As a result, the GPU will always produce exactly 60 frames per second on a 60Hz monitor. In case the GPU can’t keep up, it will reduce the frame rate to an integer divisor of 60Hz (i.e. 30, 20, etc.). The downsides of using VSync are that the frame rate can jump abruptly by a factor and it adds a considerable amount of lag, both of which can be a disadvantage or at least annoying for gaming. FastSync is a variant of VSync with frame skipping. Instead of limiting the frame rate to e.g. 60Hz, the graphics cards will keep rendering as many frames per second as it can, but will still only send a new frame to the monitor 60 times a second (the most recend frame). The advantage is a slightly lower lag than with VSync, but in return the frame skipping can lead to stutter.
The third option in the list goes the other way and aims to adjust the refresh rate of the monitor dynamically. Whereas FreeSync is for AMD graphics cards, G-Sync is only supported by NVIDIA GPUs. FreeSync is a purely software-based solution and therefore basically free of charge. It leaverages the DisplayPort adaptive sync feature. G-Sync on the other hand requires dedicated hardware inside the monitor, which is why G-Sync monitors are more expensive (between 200 and 500$ difference). Both implementations seem to work reliably, but G-Sync is generally superior in terms of input lag. Adaptive sync works within a certain range, for G-Sync it is typically between 30 and the max. supported refresh rate of the monitor.
Bottom line: If you want a tear-free image with minimal lag, then there is no way around a NVIDIA G-Sync or AMD FreeSync enabled monitor.
A few hints for those who are new to G-Sync:
- Make sure to use a DisplayPort cable to connect your monitor and enable G-Sync in the NVIDIA control panel.
- Also enable VSync in the control panel, otherwise tearing can occur if the frame rate exceeds the max. refresh rate of the monitor.
- Check out the NVIDIA pendulum demo to directly compare no sync, VSync and G-Sync (disable VSync in the control panel for this demo).
- If you want to learn more about G-Sync, visit e.g. bit-tech.net.