FreeSync 2: Low Framerate Compensation
The final key feature is low framerate compensation. This is a feature that goes hand-in-hand with adaptive sync, ensuring adaptive sync functions at every framerate from 0 FPS up to the maximum refresh rate supported by the display.
There is one simple reason why we need low framerate compensation: displays can only vary their refresh rate within a certain window, for example 48 to 144 Hz. If you wanted to run a game below the minimum supported refresh rate, say at 40 FPS when the minimum refresh is 48 Hz, normally you’d be stuck with standard screen tearing or stuttering issues like you’d get with a fixed refresh monitor. That’s because the GPU’s render rate is out of sync with the display refresh rate.
Low framerate compensation, or LFC, extends the window in which you can sync the render rate to the refresh rate using adaptive sync. When the framerate falls below the minimum refresh rate of the monitor, frames are simply displayed multiple times and the display runs at a multiple of the required refresh rate.
In our previous example, to display 40 FPS using LFC, every frame is doubled and then this output is synced to the display running at 80 Hz. You can even run games at, say, 13 FPS and have that synced to a refresh rate; in that case the monitor would run at 52 Hz (to exceed the 48 Hz minimum) and then every frame would be displayed 4 times.
The end result is LFC effectively removes the minimum refresh rate of adaptive sync displays, but for LFC to be supported, the monitor needs to have a maximum refresh rate that is at least double the minimum refresh rate. This is why not all FreeSync monitors support LFC; some come with just 48 to 75 Hz refresh windows, which doesn’t meet the criteria for LFC. However in the case of FreeSync 2, every monitor validated for this spec will support LFC so you won’t have to worry about the minimum refresh rate of the monitor.