In G-SYNC's case, less that the "New frame isn't ready, display previous frame again," and more that the low (EDIT: "high") frametimes space the frame delivery far enough apart to necessitate that those frames be refreshed more than once until the next to keep the display active. This also makes frame delivery at lower framerates visually smoother than other syncing methods, as they are refreshed at exact multiples, and as soon as they are ready.salt wrote:This is what you are saying happens to a Gsync display at sub-30fps scenarios. New frame isn't ready, display previous frame again.
With V-Sync at 30 fps/sub 30 fps scenarios (not sustained 30 fps, but drops below 60Hz with double buffer for instance), the refresh rate isn't adjusted to match the framerate, which is why the frame repeats in the first place, because it misses a delivery window, at which point it must be displayed twice. This actually causes visible stutter, as you see update, update, pause (frame displayed twice), update, update.
G-SYNC in the lower range (or any range) doesn't have this issue, because it doesn't have to wait for the next delivery window, it just displays the next frame when it's ready. There is a difference between a frame being "displayed twice" and a frame being "refreshed twice (displayed once)." V-sync does the first, G-SYNC does the latter.
Also, above 36 fps, none of this happens; G-SYNC simply adjusts the refresh rate to the literal framerate number (37 fps at 37Hz, 55 fps at 55Hz, 100 fps at 100Hz, etc).