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.



2630 Comments For “G-SYNC 101”

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alonzo_waters
Member
alonzo_waters

Hi, Amazing post I must say! I am having some trouble. I have a 1440p 240hz Gsync ultimate monitor with a 3080 & 13th gen cpu. I am trying to set up apex to run smooth so I followed this guide as in Gsync on + vsync nvcp on with vsync off in game while reflex is on & fps cap with RTSS. My game stutters no matter what with this set up when dropping out of ship regardless of my stable fps. It’s specifically when I look around. When I turn reflex off in drop ship, I can look around without any problems, very smooth.

Once I’m on the ground and playing with these settings, it continues to look very choppy when I look around. It happens when I move my mouse in a circle motion (my fps graph is stable while this happens). I also noticed when I put the command +fps_max 0 the game seems to run a little more smooth but when I delete that command, the game becomes extremely choppy while looking around.

I’m just wondering if I am doing anything wrong on my end as far as my setup? My temps are fine, background apps are not taking many resources at all & I’ve tried many optimizations with NVCP. Pretty desperate at this point as I invested good money into this setup. Thanks you advance! I really appreciate it!

NookFPS
Member
NookFPS

Yooo

Alonzo. I had the same issue and i was going crazy. I always had micro stutters and i didnt know where it was coming from. So for me its running now like this:

NVCP Vsync ON
RTSS Framerate 3 Frames under your Screen refresh rate.

Thats it. For me it was the Framerate limiter. The ingame Apex caused microstutters and the Nvidia Limiter also.

Take the first Option on this link but only with RTSS

https://blurbusters.com/gsync/gsync101-input-lag-tests-and-settings/14/

Kincior
Member
Kincior

What do you think I should run in cs go?

180 Hz with G-Sync + Vsync (NVCP) capped at 177/8 fps
or
165 Hz No Gsync, no Vsync, and uncapped fps?

On one hand I have higher refresh rate but on the other; lower latency.

billy
Member
billy

I play destiny 2 on a 240 hz monitor. I have gsync compatible monitor with in game reflex on and v sync on globally in control panel. But I still get hitches and stutters from time to time. Am I doing something wrong? My cpu is 12900k and i have 32 gb ram 3600

majkool
Member
majkool

@jorimt that’s the best article about that on the internet!

I’m right that for dynamic fps game like CS the best settings are:
G-SYNC on + VSYNC on (NVCP) + LLM on (NVCP) and fps_max 276 because of 280Hz monitor refresh rate?

Regarding input lag it seems exact the same like V-SYNC off + fps_max 276 but what is better when my fps drops below 200 fps which settings are better in input lag?

Igor
Member
Igor

Hello! I apologize for my English, I write through Google translator.
My computer configuration:
CPU: i7-8700K
Motherboard: Gigabyte Z370 AORUS Gaming K3
RAM: Kingston 32GB (2x16GB) 3000 MHz HyperX Predator
SSD: SAMSUNG 850 Pro 256GB 2.5″ SATA
Video card: MSI PCI-Ex GeForce RTX 2080 Super Gaming X Trio
Monitor: ASUS VG258Q 24.5″ 144 Hz 1920Ρ…1080 (Free Sync, supported in nVidia control panel)
Everything is clearly written in your article, but I have two questions:
1. If I set the FPS limit in the nVidia control panel to 72fps, do I need to enable vsync?
2. Some games do not disable FPS capping. For example, like in Nioh 2: minimum: 30 fps, maximum: 120 fps, what would you recommend: should I set an FPS limit? Should you enable vertical sync?
I don’t know if my questions are clear…

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