G-SYNC 101: G-SYNC Ceiling vs. FPS Limit


How Low Should You Go?

Blur Busters was the world’s first site to test G-SYNC in Preview of NVIDIA G-SYNC, Part #1 (Fluidity) using an ASUS VG248QE pre-installed with a G-SYNC upgrade kit. At the time, the consensus was limiting the fps from 135 to 138 at 144Hz was enough to avoid V-SYNC-level input lag.

However, much has changed since the first G-SYNC upgrade kit was released; the Minimum Refresh Range wasn’t in place, the V-SYNC toggle had yet to be exposed, G-SYNC did not support borderless or windowed mode, and there was even a small performance penalty on the Kepler architecture at the time (Maxwell and later corrected this).

My own testing in my Blur Busters Forum thread found that just 2 FPS below the refresh rate was enough to avoid the G-SYNC ceiling. However, now armed with improved testing methods and equipment, is this still the case, and does the required FPS limit change depending on the refresh rate?

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, just 2 FPS below the refresh rate is indeed still enough to avoid the G-SYNC ceiling and prevent V-SYNC-level input lag, and this number does not change, regardless of the maximum refresh rate in use.

To leave no stone unturned, an “at” FPS, -1 FPS, -2 FPS, and finally -10 FPS limit was tested to prove that even far below -2 FPS, no real improvements can be had. In fact, limiting the FPS lower than needed can actually slightly increase input lag, especially at lower refresh rates, since frametimes quickly become higher, and thus frame delivery becomes slower due to the decrease in sustained framerates.

As for the “perfect” number, going by the results, and taking into consideration variances in accuracy from FPS limiter to FPS limiter, along with differences in performance from system to system, a -3 FPS limit is the safest bet, and is my new recommendation. A lower FPS limit, at least for the purpose of avoiding the G-SYNC ceiling, will simply rob frames.



2231 Comments For “G-SYNC 101”

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Vasko
Member
Vasko

Hello,

Would you please recommend the lowest latency setting for my pc in COD Cold War? I have the 360Hz Asus monitor and get between 280-310 fps during game play. I currently have the monitor set at 240Hz with unlimited fps, V-Sync and G-Sync off and it is very smooth. Would it be better to change the refresh rate to 300 or 360Hz even though the fps most likely average around 280? Does it make sense to turn G-Sync on?

Your help is highly appreciated!

Thank you,
Vasko

Tonaway
Member
Tonaway

Hello, I have a weird question.

Does G-SYNC still work if you lower the refresh rate (to something inside G-SYNC range) and use V-SYNC on in order to lock the FPS? Instead of running max refresh rate + V-SYNC on + -3 FPS lock.

For example: set refresh rate from 144hz to 120hz and activate V-SYNC so the game runs at 120 FPS and hz. In this case, will G-SYNC still be active? Or do you still have to set a FPS limiter to 117 FPS?

Will these settings have G-SYNC working as intended or will there be detriments to running games like this (except for running it at 120hz and 120 FPS, instead of 144hz and 141 FPS). If it works, does locking the FPS this way have any benefit over other ways of locking the FPS, and does it introduce normal V-SYNC latency if it hits 120 FPS?

fatehasfans
Member
fatehasfans

Hi there, is there an optimizing guide for Free-sync?

gaxode9376
Member
gaxode9376

what if a game only let you cap at a fixed refresh rate or unlimited rather than a custom value

DerConnor
Member
DerConnor

So what actually causes the tearing from “Upper & Lower Frametime Variances”? Is it because G-Sync is somehow unable to respond to a quick change in frametime (I read somewhere it uses a fixed polling frequency to update the current refresh rate)? And in the Valorant clips with the FPS capped to 142, shouldn’t this result in a constant frametime or is there some problem with how the FPS limiter works (introducing inconsistent frametimes)? I also can’t for the life of me see any tearing in the second Valorant clip.

Thanks a lot for this article, it was a super interesting and informative read.

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