G-Sync treats this “below the window” scenario very differently. Rather than reverting to VSync on or off, the module in the G-Sync display is responsible for auto-refreshing the screen if the frame rate dips below the minimum refresh of the panel that would otherwise be affected by flicker. So, in a 30-144 Hz G-Sync monitor, we have measured that when the frame rate actually gets to 29 FPS, the display is actually refreshing at 58 Hz, each frame being “drawn” one extra instance to avoid flicker of the pixels but still maintains a tear free and stutter free animation. If the frame rate dips to 25 FPS, then the screen draws at 50 Hz. If the frame rate drops to something more extreme like 14 FPS, we actually see the module quadruple drawing the frame, taking the refresh rate back to 56 Hz. It’s a clever trick that keeps the VRR goals and prevents a degradation of the gaming experience. But, this method requires a local frame buffer and requires logic on the display controller to work. Hence, the current implementation in a G-Sync module.
But what happens with this FreeSync monitor and theoretical G-Sync monitor below the window? AMD’s implementation means that you get the option of disabling or enabling VSync. For the 34UM67 as soon as your game frame rate drops under 48 FPS you will either see tearing on your screen or you will begin to see hints of stutter and judder as the typical (and previously mentioned) VSync concerns again crop their head up. At lower frame rates (below the window) these artifacts will actually impact your gaming experience much more dramatically than at higher frame rates (above the window).