G-SYNC 101: Range


Blur Buster's G-SYNC 101: Range Chart

Exceeds G-SYNC Range

G-SYNC + V-SYNC “Off”:
G-SYNC disengages, tearing begins display wide, no frame delay is added.

G-SYNC + V-SYNC “On”:
G-SYNC reverts to V-SYNC behavior when it can no longer adjust the refresh rate to the framerate, 2-6 frames (typically 2 frames; approximately an additional 33.2ms @60 Hz, 20ms @100 Hz, 13.8ms @144 Hz, etc) of delay is added as rendered frames begin to over-queue in both buffers, ultimately delaying their appearance on-screen.

G-SYNC + Fast Sync*:
G-SYNC disengages, Fast Sync engages, 0-1 frame of delay is added**.
*Fast Sync is best used with framerates in excess of 2x to 3x that of the display’s maximum refresh rate, as its third buffer selects from the “best” frame to display as the final render; the higher the sample rate, the better it functions. Do note, even at its most optimal, Fast Sync introduces uneven frame pacing, which can manifest as recurring microstutter.
**Refresh rate/framerate ratio dependent (see G-SYNC 101: G-SYNC vs. Fast Sync).

Within G-SYNC Range

Refer to “Upper & Lower Frametime Variances” section below…

Upper & Lower Frametime Variances

G-SYNC + V-SYNC “Off”:
The tearing inside the G-SYNC range with V-SYNC “Off” is caused by sudden frametime variances output by the system, which will vary in severity and frequency depending on both the efficiency of the given game engine, and the system’s ability (or inability) to deliver consistent frametimes.

G-SYNC + V-SYNC “Off” disables the G-SYNC module’s ability to compensate for sudden frametime variances, meaning, instead of aligning the next frame scan to the next scanout (the process that physically draws each frame, pixel by pixel, left to right, top to bottom on-screen), G-SYNC + V-SYNC “Off” will opt to start the next frame scan in the current scanout instead. This results in simultaneous delivery of more than one frame in a single scanout (tearing).

In the Upper FPS range, tearing will be limited to the bottom of the display. In the Lower FPS range (<36) where frametime spikes can occur (see What are Frametime Spikes?), full tearing will begin.

Without frametime compensation, G-SYNC functionality with V-SYNC “Off” is effectively “Adaptive G-SYNC,” and should be avoided for a tear-free experience (see G-SYNC 101: Optimal Settings & Conclusion).

G-SYNC + V-SYNC “On”:
This is how G-SYNC was originally intended to function. Unlike G-SYNC + V-SYNC “Off,” G-SYNC + V-SYNC “On” allows the G-SYNC module to compensate for sudden frametime variances by adhering to the scanout, which ensures the affected frame scan will complete in the current scanout before the next frame scan and scanout begin. This eliminates tearing within the G-SYNC range, in spite of the frametime variances encountered.

Frametime compensation with V-SYNC “On” is performed during the vertical blanking interval (the span between the previous and next frame scan), and, as such, does not delay single frame delivery within the G-SYNC range and is recommended for a tear-free experience (see G-SYNC 101: Optimal Settings & Conclusion).

G-SYNC + Fast Sync:
Upper FPS range: Fast Sync may engage, 1/2 to 1 frame of delay is added.
Lower FPS range: see “V-SYNC ‘On'” above.

What are Frametime Spikes?

Frametime spikes are an abrupt interruption of frames output by the system, and on a capable setup running an efficient game engine, typically occur due to loading screens, background asset streaming, shader compilation, network activity, and/or the triggering of a script or physics system, but can also be exacerbated by an incapable setup, inefficient game engine, poor netcode, low RAM/VRAM and page file over usage, misconfigured (or limited game support for) SLI setups, faulty drivers, specific or excess background processes, in-game overlay or input device conflicts, or a combination of them all.

Not to be confused with other performance issues, like framerate slowdown or V-SYNC-induced stutter, frametime spikes manifest as the occasional hitch or pause, and usually last for mere micro to milliseconds at a time (seconds, in the worst of cases), plummeting the framerate to as low as the single digits, and concurrently raising the frametime to upwards of 1000ms before re-normalizing.

G-SYNC eliminates traditional V-SYNC stutter caused below the maximum refresh rate by repeated frames from delayed frame delivery, but frametime spikes still affect G-SYNC, since it can only mirror what the system is outputting. As such, when G-SYNC has nothing new to sync to for a frame or frames at a time, it must repeat the previous frame(s) until the system resumes new frame(s) output, which results in the visible interruption observed as stutter.

The more efficient the game engine, and the more capable the system running it, the less frametime spikes there are (and the shorter they last), but no setup can fully avoid their occurrence.

Minimum Refresh Range

Once the framerate reaches the approximate 36 and below mark, the G-SYNC module begins inserting duplicate refreshes per frame to maintain the panel’s minimum physical refresh rate, keep the display active, and smooth motion perception. If the framerate is at 36, the refresh rate will double to 72 Hz, at 18 frames, it will triple to 54 Hz, and so on. This behavior will continue down to 1 frame per second.

Regardless of the reported framerate and variable refresh rate of the display, the scanout speed will always be a match to the display’s current maximum refresh rate; 16.6ms @60Hz, 10ms @100 Hz, 6.9ms @144 Hz, and so on. G-SYNC’s ability to detach framerate and refresh rate from the scanout speed can have benefits such as faster frame delivery and reduced input lag on high refresh rate displays at lower fixed framerates (see G-SYNC 101: Hidden Benefits of High Refresh Rate G-SYNC).



1873 Comments For “G-SYNC 101”

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blaskovic
Member
blaskovic

Hi jorimt. I have a question for you. Sometime in older games (2011 – 2013) I have a drop frame from 144 to 140 or 144 to 135 and I notice this microstutter with G-sync but in other games if I have this drops (for example in Dirty Rally) I don’t see anything. My question is this: Why in some case (games) G-Sync seems works but in other circumstances (games) i see this microstutter? G-Sync shouldn’t avoid Microstutter? Thank you

stadiofriuli
Member
stadiofriuli

I’ve got a question. Got the Dell S2721DGF(A) which is G-Sync compatible, I’m running the monitor at 165Hz.

So what I basically did is to set a FPS cap @161 with RTSS.

Enabled G-Sync fullscreen in NVCP.

Enabled V-Sync in NVCP.

According to the guide V-Sync within the G-Sync range should still act like for native G-Sync monitors when it’s an official supported G-Sync compatible monitor.

What happens for me though is.

When V-Sync is enabled FPS cap at 158, not 161 as set in RTSS.

When I then disable V-Sync and have only G-Sync running it’s capped at 161 again.

So my question really is why this weird behaviour?

Should I activate or deactivate V-Sync in my case?

SvenL
Member
SvenL

Hi,
First of all, thank you so much for creating such an amazing guide. After reading through a few more questions arose.

I’m playing Warzone (FPS game) on a 1080p 144hz free sync monitor with an RTX 2080Ti graphics card. (I achieve 170-180 fps in game uncapped, which is above the refresh rate of my monitor)

My goal is to have a 100% tear-free gaming experience with the least amount of input lag to achieve the best possible accuracy.

First, I took over the following settings from you
NVCP: G-Sync & V-Sync: On

But when it comes to the FPS limiter, I’m still unsure which is best in my case. (Warzone also supports reflex)

In-Game FPS Limiter (141 FPS cap)
Reflex: On / On + Boost
RTSS / NVIDIA’s Max Frame Rate (141 FPS cap)

The question is which of these options has the lowest input lag and at the same time the most constant possible frame time. (I assume these 2 factors are especially important for FPS games)
Or what you think would be the best sweet spot out of all of these options.

With reflex activated (On + Boost), I noticed that the frame rate varies (around 138 fps). I’m not sure whether this will have a negative impact on my frame time or input delay, as I could easily achieve a constant 141 FPS with my graphics card. Should I then prefer the in-game FPS limiter or RTSS / NVIDIA’s Max Frame Rate over reflex?

Thank you very much

RoseGoldCrobat
Member
RoseGoldCrobat

I signed up here since you seem to know a lot about this. I have a very strange issue.

I have a monitor that is Gsync compatible and Gsync is on in fullscreen mode.

When I play certain games, the current ones I’ve seen it in are Red Dead Redemption 2 and Hitman 3 I would like to have gsync on and vsync on. The problem is when both settings are on at the same time my FPS caps to 72 fps, half of my monitor’s refresh rate. I don’t understand why this is happening. Could I be missing a setting?

Zehdah
Member
Zehdah

Hello. I have a new monitor, it’s a Samsung G7 Odyssey which is 1440p 240hz with Gsync. I’m wondering what you would recommend for optimal performance/gaming with that setup since it’s unlikely I will hit 240hz in a game at 1440p with a 1080ti, should I still follow the above instructions and cap to 237 along with vsync on in CP, off in game? Curious if there’s any extra things I need to do.

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