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.



576 Comments For “G-SYNC 101”

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Zehdah
Member
Zehdah

If I get a 240 Hz monitor, like the BenQ ZOWIE XL2546, should I still be using the method above (Gsync on, Vsync off in game, on in control panel and cap FPS to 237 with RTSS) or should I uncap my framerate with Vsync and Gsync off? The reason I ask is a lot of pros in FPS games such as Apex, Siege, CSGO, seem to do the latter and I can’t understand why, unless G-sync isn’t available on those monitors, but I read that G-sync is available on freesync monitor’s now with 10xx and above cards, am I wrong? Greatly appreciate any input!

DanWensing
Member
DanWensing

Which one has the lowest input lag?
1. Gsync + Vsync + Low Latency Mode at Ultra (no fps limit)
2. Gsync + Vsync + NVC/RTSS fps limit (3fps below Refresh rate)

DanWensing
Member
DanWensing

Hi, I understand that we should use Vsync On when using Gsync. But with the new LG OLED C9, which is gsync compatible, if I have Vsync “ON” I get some microstutter every 10s or so. But if I keep vsync off, the game is 100% smooth (I have the FPS capped at 3fps below the TVs refresh rate). One friend of mine has the same issue with his C9. Do you know why this is happening?

BlackStorm82
Member
BlackStorm82

(Gsync off/Gsync not supported) 144hz 144fps CAP(ingame) (no v-sync) this

144hz 139fps cap(ingame) (no v-sync)
Is it correct to lose input lag than condition?

If I turn off v-sync, is it the same as 139 or 144 cap?
Is a 139fps limit good for 144hz even on a regular monitor? in a v-sync off.
Sorry for the beginner. i love blurbusters

ezidifn
Member
ezidifn

i have a 144hz AMD freesync monitor. How should i get the leasy amount pf input lah? By enabling G sync on nvidia and cap hz at 142/141?

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