G-SYNC 101: G-SYNC vs. V-SYNC w/FPS Limit


So Close, Yet So Far Apart

On the subject of single, tear-free frame delivery, how does standalone double buffer V-SYNC compare to G-SYNC with the same framerate limit?

Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings

As the results show, but for 60Hz (remember, a “frame” of delay is relative to the refresh rate), the numbers are relatively close. So what’s so great about G-SYNC’s ability to adjust the refresh rate to the framerate, if the majority of added input latency with V-SYNC can be eliminated with a simple FPS limit? Well, as the title of this section hints, it’s not quite that cut and dry…

While it’s common knowledge that limiting the FPS below the refresh rate with V-SYNC prevents the over-queuing of frames, and thus majority of added input latency, it isn’t without its downsides.

Unlike G-SYNC, V-SYNC must attempt to time frame delivery to the fixed refresh rate of the display. If it misses a single one of these delivery windows below the maximum refresh rate, the current frame must repeat once until the next frame can be displayed, locking the framerate to half the refresh rate, causing stutter. If the framerate exceeds the maximum refresh rate, the display can’t keep up with frame output, as rendered frames over-queue in both buffers, and appearance of frames is delayed yet again, which is why an FPS limit is needed to prevent this in the first place.

When an FPS limit is set with V-SYNC, the times it can deliver frames per second is shrunk. If, for instance, the FPS limiter is set to 59 fps on a 60Hz display, instead of 60 frames being delivered per second, only 59 will be delivered, which means roughly every second a frame will repeat.

As the numbers show, while G-SYNC and V-SYNC averages are close over a period of frames, evident by the maximums, it eventually adds up, causing 1/2 to 1 frame of accumulative delay, as well as recurring stutter due to repeated frames. This is why it is recommended to set a V-SYNC FPS limit mere decimals below the refresh rate via external programs such as RTSS.

That said, an FPS limit is superior to no FPS limit with double buffer V-SYNC, so long as the framerate can be sustained above the refresh rate at all times. However, G-SYNC’s ability to adjust the refresh rate to the framerate eliminates this issue entirely, and, yet again, beats V-SYNC hands down.



251 Comments For “G-SYNC 101”

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Savatgy
Member
Savatgy

NO matter how I configure G Sync, it appears to cause input lag in Overwatch.

Chief Blur Buster
Admin

Which monitor model? And G-SYNC native or G-SYNC compatible (FreeSync)?

Karker
Member
Karker

so functionally and properly setup, gsync and quite possibly gsync-compatible* should have lower input lag than even an uncapped frame rate?

if this is the case, why arent competitive gamers doing this?

ivandudude
Member
ivandudude

should i cap it to 141 if i have a 144hz monitor with v sync on or off? also i dont have g sync but im looking to get the less input lag. this is for fortnite and this game called smite.

bioinfinite121818
Member
bioinfinite121818

Hi, I was wondering I recently bought a g sync 240hzmonitor and I have g sync and nvidia v sync on, should I lower the refresh rate of my monitor 237 or is okay if I can keep it at 240?

rayjays1986
Member
rayjays1986

Was wondering, do you have any advice on State of Decay 2? I seem to be having major stutter/lag issues with that game and G-Sync. It’s hard to explain, it’s almost as if there’s some sort of asset loading going on while I’m driving especially, and it looks quite laggy/stuttery. I have seen numerous others talk of this, and numerous others who say it runs smooth as butter. I change over to fixed refresh and vsync, and it seems to help a little, but it’s not totally gone. BUT, using fixed refresh w/ fast sync, it almost (not quite but almost) eliminates the effect, with the lag much less apparent. I experimented a bit and G-sync plus fast sync seems to help too, though here it says not to do that. I wouldn’t think of doing that in anything else, I just seen several posts that it had something to do w/ that game/engine in particular w/ G-sync and laggy/stuttery moments on occasion. Did you (or anyone else here) happen to experience any of this with State of Decay 2? If so, anyone know how to fix it? I actually really enjoy the game, but that lag is incredibly annoying for me (seems to happen most when I’m driving). Thanks in advance for any answers!

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