G-SYNC 101: G-SYNC vs. V-SYNC OFF


Beyond the Limits of the Scanout

It’s already been established that single, tear-free frame delivery is limited by the scanout, and V-SYNC OFF can defeat it by allowing more than one frame scan per scanout. That said, how much of an input lag advantage can be had over G-SYNC, and how high must the framerate be sustained above the refresh rate to diminish tearing artifacts and justify the difference?

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

Quite high. Counting first on-screen reactions, V-SYNC OFF already has a slight input lag advantage (up to a 1/2 frame) over G-SYNC at the same framerate, especially the lower the refresh rate, but it actually takes a considerable increase in framerate above the given refresh rate to widen the gap to significant levels. And while the reductions may look significant in bar chart form, even with framerates in excess of 3x the refresh rate, and when measured at middle screen (crosshair-level) only, V-SYNC OFF actually has a limited advantage over G-SYNC in practice, and most of it is in areas that one could argue, for the average player, are comparatively useless when something such as a viewmodel’s wrist is updated 1-3ms faster with V-SYNC OFF.

This is where the refresh rate/sustained framerate ratio factors in:

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 shown in the above diagrams, the true advantage comes when V-SYNC OFF can allow not just two, but multiple frame scans in a single scanout. Unlike syncing solutions, with V-SYNC OFF, the frametime is not paced to the scanout, and a frame will begin scanning in as soon as it’s rendered, regardless whether the previous frame scan is still in progress. At 144Hz with 1000 FPS, for instance, this means with a sustained frametime of 1ms, the display updates nearly 7 times in a single scanout.

In fact, at 240Hz, first on-screen reactions became so fast at 1000 FPS and 0 FPS, that the inherit delay in my mouse and display became the bottleneck for minimum measurements.

So, for competitive players, V-SYNC OFF still reigns supreme in the input lag realm, especially if sustained framerates can exceed the refresh rate by 5x or more. However, while at higher refresh rates, visible tearing artifacts are all but eliminated at these ratios, it can instead manifest as microstutter, and thus, even at its best, V-SYNC OFF still can’t match the consistency of G-SYNC frame delivery.



347 Comments For “G-SYNC 101”

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dotyerts
Member
dotyerts

I’ve been reading your stuff for years. Appreciate all of it.
Let me get this summarized in one quick writeup.

I have a freesync compatible monitor viotek gft27db 144hz. If i enable G-SYNC properly with my DP cable on an RTX 2070, and have VSYNC ON, as well as + NULL, then I should
1. be all good in terms of enabling GSYNCwithout the issues of VSYNC off causing tearing sometimes.
2. NOT be required to Limit my fps to 141 by using RTSS? I’m currently using it limited to 141 to stay under and avoid the buffer flip interval.
2.b. wondering if this is the case, so I can turn off RTSS and retrieve that minuscule amount of input lag it causes.

nuk_won
Member
nuk_won

Tell me if I am wrong. But I think I figured it out. G-sync it self don’t ad input lag so if i have it I might as well turn it on to get stutter/screen tearing free game play. So as I understand u turn g-sync on + vsync off find the fps by caping it 165 then 164 ect where there is no screen tearing at bottom of the screen let’s say it would be 158 then u go Nvidia control panel turn g-sync on vsync off set low latency to ultra and cap ur fps at 158 and this is the way u get lowest input lag + as it would be running a monitor who don’t have g-sync and just caping fps at 165fps but this way u don’t get the benefits as smooth game play no stuttering. This would be best only for GPU bound games like apex legends other games that use CPU this could increase input lag? Please correct me if I’m wrong or maybe I need to turn g-sync off set fixed refresh rate null set to ultra fps cap at 165. Main game is apex legends. This I how I run the game currently.

Specs pc: 87k at 4.5gh 1080ti oc. Monitor: AOC 24″ 2k rez 165hz g-sync.

Ownsin
Member
Ownsin

Hey there. Can I ask If I should turn on V-Sync in-game or from the Nivida Control Panel for my G-Sync 144hz monitor? I recently watched a video for Battlenonesene where he says turning on V-Sync inside of games is better than turning it on from the NVCP because some engines have optimizations for their V-Sync. What’s your take on this matter?

Another thing I want to bring up. Can you tell me what’s the difference between turning on V-Sync and Fastsync from the NVCP? as far as I know, Fastsync eliminates tearing, leaves the frame rate unlocked and doesn’t add nearly as much input lag as regular V-Sync, so why is it recommended that we use V-Sync instead of Fastsync?

P.S: which frame limiter do you suggest I should use.

Thank you.

gzmm
Member
gzmm

Hello, i have a samsung C24FG73, with 70~144hz freesync range.
for me, gsync+vsync in driver with 138 fps limiter seens to be working very well.
but, if a game is locked at 60 frames, the gsync will be ‘disable’, and only vsync will work, correct?
this will introduce alot of input lag, or the FLC helps?

buddersnaps
Member
buddersnaps

Hi when running a game that GPU is using 100% resources do i still want NVCP v sync set ON and low latency set to Ultra. i have g sync monitor thats 144hz. i have games capped at 141 but get about 100 – 120 most of the time. are my settings still correct when getting frames below monitor refresh rate and GPU bound using NVCP v sync ON, low latency ULTRA, Gsync ON, and in game fps capped to 141 and vsync off?

then to clarify when not gpu bound just use the “on” option instead of ultra for low latency?

also monitor has ULMB or should i just stick with gsync? if i used ULMB what would i do for vsync and latency options?

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