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


At the Mercy of the Scanout

Now that the FPS limit required for G-SYNC to avoid V-SYNC-level input lag has been established, how does G-SYNC + V-SYNC and G-SYNC + V-SYNC “Off” compare to V-SYNC OFF at the same framerate?

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

The results show a consistent difference between the three methods across most refresh rates (240Hz is nearly equalized in any scenario), with V-SYNC OFF (G-SYNC + V-SYNC “Off,” to a lesser degree) appearing to have a slight edge over G-SYNC + V-SYNC. Why? The answer is tearing…

With any vertical synchronization method, the delivery speed of a single, tear-free frame (barring unrelated frame delay caused by many other factors) is ultimately limited by the scanout. As mentioned in G-SYNC 101: Range, The “scanout” is the total time it takes a single frame to be physically drawn, pixel by pixel, left to right, top to bottom on-screen.

With a fixed refresh rate display, both the refresh rate and scanout remain fixed at their maximum, regardless of framerate. With G-SYNC, the refresh rate is matched to the framerate, and while the scanout speed remains fixed, the refresh rate controls how many times the scanout is repeated per second (60 times at 60 FPS/60Hz, 45 times at 45 fps/45Hz, etc), along with the duration of the vertical blanking interval (the span between the previous and next frame scan), where G-SYNC calculates and performs all overdrive and synchronization adjustments from frame to frame.

The scanout speed itself, both on a fixed refresh rate and variable refresh rate display, is dictated by the current maximum refresh rate of the display:

Blur Buster's G-SYNC 101: Scanout Speed DiagramAs the diagram shows, the higher the refresh rate of the display, the faster the scanout speed becomes. This also explains why V-SYNC OFF’s input lag advantage, especially at the same framerate as G-SYNC, is reduced as the refresh rate increases; single frame delivery becomes faster, and V-SYNC OFF has less of an opportunity to defeat the scanout.

V-SYNC OFF can defeat the scanout by starting the scan of the next frame(s) within the previous frame’s scanout anywhere on screen, and at any given time:

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

This results in simultaneous delivery of more than one frame scan in a single scanout (tearing), but also a reduction in input lag; the amount of which is dictated by the positioning and number of tearline(s), which is further dictated by the refresh rate/sustained framerate ratio (more on this later).

As noted in G-SYNC 101: Range, G-SYNC + VSYNC “Off” (a.k.a. Adaptive G-SYNC) can have a slight input lag reduction over G-SYNC + V-SYNC as well, since it will opt for tearing instead of aligning the next frame scan to the next scanout when sudden frametime variances occur.

To eliminate tearing, G-SYNC + VSYNC is limited to completing a single frame scan per scanout, and it must follow the scanout from top to bottom, without exception. On paper, this can give the impression that G-SYNC + V-SYNC has an increase in latency over the other two methods. However, the delivery of a single, complete frame with G-SYNC + V-SYNC is actually the lowest possible, or neutral speed, and the advantage seen with V-SYNC OFF is the negative reduction in delivery speed, due to its ability to defeat the scanout.

Bottom-line, within its range, G-SYNC + V-SYNC delivers single, tear-free frames to the display the fastest the scanout allows; any faster, and tearing would be introduced.



2778 Comments For “G-SYNC 101”

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ULA
Member
ULA

Hi there!

First of all, thanks for the guide! helped a lot.

Now, to my question. I am looking to play Cyberpunk with the path-tracing settings, which is obviously a computional nightmare—even for my 4090. This would be the first time I will enable DLSS 3.0, which I will refer to as frame-generation (FG) from here on it. I will be using the perfomance-mode of DLSS 2.0, since I game at 4k and I want to mininze the input lag from FG; I believe the higher the native frame rate, the lower the input delay due to FG.

Now, from what I know, is that I should still enable V-sync from the NVIDIA control pannel. However, it is not needed to set the frame rate 3FPS below the monitor’s refersh rate, since that is automatically done by Reflex (which will be enabled by default when using FG).

However, I would still like to cap my frame rate below my native 120FPS, say at 100FPS, so that the frame rate is consistent. But, I noticed that the frame-rate limiter (both in-game and in the NVIDIA control panel) has zero affect. Is this beheviour expected?

Dogelol
Member
Dogelol

I used the Gsync on – Vsync on (in NVCP) and frame rate cap to 160 (165hz max) from RTSS however I experience varying degrees of flickering in menus mostly but in some games too.

From what I know there is no way to fix the flickering as it is something normal for VA/OLED’s.

My question is if I can not detect tearing (most likely there is some but either high fps/oled smoothness or simply my eyes not detecting it)

I am thinking about playing with Gsync off and no vsync on and just an fps cap. Would that impact my experience?

Ideally I would like to keep gsync on due to the smoothness I feel with it however the flickering is a deal breaker for me.

What is the best combination if I do not wish to use Gsync, should I keep vsync and fps cap, or only the fps cap?

Thank you!

august
Member
august

best settings for eafc 24?

rec0veryyy
Member
rec0veryyy

hi, i have been playing cs2 for several weeks, my monitor is 1440p 144hz with gsync compatible, in the nvcp i have gsync on + vsync on, i also limit the fps to 141 inside the nvcp, then inside the game vsync off and the nvidia reflex off, i get 138fps as expected and everything works fine, but i have a question, should i play like this or disable the vsync in the nvcp for cs2 to go to 200 or 300fps? because as I understand the more fps the less frametime in ms, now I would have about 7.2ms but if I unlimit it and I go to 250fps I would have 4ms, is this really so and would it make any difference?

HarmVJ
Member
HarmVJ

So windows 10 has something called VRR in the graphics setting. Should it be used in tandem with G-Sync + NVCP Vsync. Some sources and review just say to turn it on along with g-sync.

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