G-SYNC 101: G-SYNC Ceiling vs. V-SYNC


Identical or Fraternal?

As described in G-SYNC 101: Range, G-SYNC doesn’t actually become double buffer V-SYNC above its range (nor does V-SYNC take over), but instead, G-SYNC mimics V-SYNC behavior when it can no longer adjust the refresh rate to the framerate. So, when G-SYNC hits or exceeds its ceiling, how close is it to behaving like standalone V-SYNC?

Pretty close. However, the G-SYNC numbers do show a reduction, mainly in the minimum and averages across refresh rates. Why? It boils down to how G-SYNC and V-SYNC behavior differ whenever the framerate falls (even for a moment) below the maximum refresh rate. With double buffer V-SYNC, a fixed frame delivery window is missed and the framerate is locked to half the refresh rate by a repeated frame, maintaining extra latency, whereas G-SYNC adjusts the refresh rate to the framerate in the same instance, eliminating latency.

As for “triple buffer” V-SYNC, while the subject won’t be delved into here due to the fact that G-SYNC is based on a double buffer, the name actually encompasses two entirely separate methods; the first should be considered “alt” triple buffer V-SYNC, and is the method featured in the majority of modern games. Unlike double buffer V-SYNC, it prevents the lock to half the refresh rate when the framerate falls below it, but in turn, adds 1 frame of delay over double buffer V-SYNC when the framerate exceeds the refresh rate; if double buffer adds 2-6 frames of delay, for instance, this method would add 3-7 frames.

“True” triple buffer V-SYNC, like “alt,” prevents the lock to half the refresh rate, but unlike “alt,” can actually reduce V-SYNC latency when the framerate exceeds the refresh rate. This “true” method is rarely used, and its availability, in part, can depend on the game engine’s API (OpenGL, DirectX, etc).

A form of this “true” method is implemented by the DWM (Desktop Window Manager) for borderless and windowed mode, and by Fast Sync, both of which will be explained in more detail further on.

Suffice to say, even at its worst, G-SYNC beats V-SYNC.



172 Comments For “G-SYNC 101”

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Member
king37

Very helpful

Member
besweeet

To confirm, G-SYNC ON + v-sync ON is better than G-SYNC OFF + v-sync ON? My ultimate goal is to eliminate tearing while not introducing input lag, so it seems like the former is the way to go.

Member
hkeep

Thank you for those detailed explanations. My question is why would we enable v-sync if it would never reach the refresh rate cap with the rtss. And also, if for example, I am consistently running the game at a higher refresh rate than my monitor (which is 120hz), what is the point of rtss if it would limit my fps to 2-3 frames below the refresh rate? Shouldn’t I just enable G-sync without a limit which as you said has less input lag than v-sync even when the fps goes over the refresh rate. Which brings to the question of why do we need v-sync at all?

Member
Dragonite

I have the Viewsonic VX2458-C-mhd which is a Freesync monitor. Since my GPU is GTX 1080 i could enable G-sync with the latest drivers. But the problem is that i have brightness flickering (which i read that is a quite frequent occurrence to all adaptive sync technologies). Since i tried to fix it but nothing worked i disabled Freesync/G-sync. So the question is, now that G-sync is off, should i just enable V-sync (NCP) + framelimit for better visual quality and prevent tearing or leave V-sync (NCP) off but still use framelimit?

Member
hyrnos

Hi, thanks for the excellent guide

I want to play games that are capped to 60 ish fps by their game engine, should i enable vsync? (assassin’s creed) I ofc want to enable gsync

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