G-SYNC 101: In-game vs. External FPS Limiters


Closer to the Source*

*As of Nvidia driver version 441.87, Nvidia has made an official framerate limiting method available in the NVCP; labeled “Max Frame Rate,” it is a CPU-level FPS limiter, and as such, is comparable to the RTSS framerate limiter in both frametime performance and added delay. The Nvidia framerate limiting solutions tested below are legacy, and their results do not apply to the “Max Frame Rate” limiter.

Up until this point, an in-game framerate limiter has been used exclusively to test FPS-limited scenarios. However, in-game framerate limiters aren’t available in every game, and while they aren’t required for games where the framerate can’t meet or exceed the maximum refresh rate, if the system can sustain the framerate above the refresh rate, and a said option isn’t present, an external framerate limiter must be used to prevent V-SYNC-level input lag instead.

In-game framerate limiters, being at the game’s engine-level, are almost always free of additional latency, as they can regulate frames at the source. External framerate limiters, on the other hand, must intercept frames further down the rendering chain, which can result in delayed frame delivery and additional input latency; how much depends on the limiter and its implementation.

RTSS is a CPU-level FPS limiter, which is the closest an external method can get to the engine-level of an in-game limiter. In my initial input lag tests on my original thread, RTSS appeared to introduce no additional delay when used with G-SYNC. However, it was later discovered disabling CS:GO’s “Multicore Rendering” setting, which runs the game on a single CPU-core, caused the discrepancy, and once enabled, RTSS introduced the expected 1 frame of delay.

Seeing as the CS:GO still uses DX9, and is a native single-core performer, I opted to test the more modern “Overwatch” this time around, which uses DX11, and features native multi-threaded/multi-core support. Will RTSS behave the same way in a native multi-core game?

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

Yes, RTSS still introduces up to 1 frame of delay, regardless of the syncing method, or lack thereof, used. To prove that a -2 FPS limit was enough to avoid the G-SYNC ceiling, a -10 FPS limit was tested with no improvement. The V-SYNC scenario also shows RTSS delay stacks with other types of delay, retaining the FPS-limited V-SYNC’s 1/2 to 1 frame of accumulative delay.

Next up is Nvidia’s FPS limiter, which can be accessed via the third-party “Nvidia Inspector.” Unlike RTSS, it is a driver-level limiter, one further step removed from engine-level. My original tests showed the Nvidia limiter introduced 2 frames of delay across V-SYNC OFF, V-SYNC, and G-SYNC scenarios.

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

Yet again, the results for V-SYNC and V-SYNC OFF (“Use the 3D application setting” + in-game V-SYNC disabled) show standard, out-of-the-box usage of both Nvidia’s v1 and v2 FPS limiter introduce the expected 2 frames of delay. The limiter’s impact on G-SYNC appears to be particularly unforgiving, with a 2 to 3 1/2 frame delay due to an increase in maximums at -2 FPS compared to -10 FPS, meaning -2 FPS with this limiter may not be enough to keep it below the G-SYNC ceiling at all times, and it might be worsened by the Nvidia limiter’s own frame pacing behavior’s effect on G-SYNC functionality.

Needless to say, even if an in-game framerate limiter isn’t available, RTSS only introduces up to 1 frame of delay, which is still preferable to the 2+ frame delay added by Nvidia’s limiter with G-SYNC enabled, and a far superior alternative to the 2-6 frame delay added by uncapped G-SYNC.



2686 Comments For “G-SYNC 101”

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Singularafk
Member
Singularafk

Hello. There are a few things I didn’t understand from the article and I would like to ask about them. I have a PG32UQX monitor with Gsync ultimate. I didn’t understand how it is with the Vsync setting. Should I rather use it on this monitor in game or in nvidia panel settings. So which is better for Gsync. And if I set vsync in the nvidia panel (which means I have my own 3d settings) will it change the look of the game ? Like texture quality and stuff. And the second thing. How about the windows power plan. Is it ok to use balance or is high/ultimate perfromance better ? Thanks..

mano4261
Member
mano4261

I play valorant and want to know the best possible way to optimize my game for input lag. Please answer by letting me know what to do with the following settings: G sync on vs off, V sync on vs off, Nvidia Reflex on vs off, and fps cap. Thank you 🙂 I have 3080 and 5600x

GGGQEP
Member
GGGQEP

Hello, I have an ASUS PG279QM monitor. This monitor has an FPS Counter feature with a graph displaying current frame rate. While testing with a Nvidia CP VSYNC ON + NVIDIA CP FPS LIMITER set to 237 FPS in a CS:GO game I’ve noticed that most of the time it is at 237-238 but sometimes it spikes to 240 on that “FPS Counter” graph, so does it mean that GSync is disabled and VSYNC and its latency is enabled in that case? I tried to cap it to 235 fps and still sometimes it shows me 240, I tried to lower it to 230 fps and then I didn’t noticed these spikes to 240 on that graph on my monitor. Right now I’m not sure whether I should stick to 237 FPS or to 230 because I mainly concerned whether Gsync may be disabled in that “spike case”, but I’m not sure maybe it is just a graph that is not very precise? What is your opinion on this? Also, I’ve tried to use an “In game” limiter in CS:GO but it is far less consistent compared to NVidia’s one. I’ve read articles and it is said that the recommendation is to set it to “-3 FPS” but in my case I’m not sure. What’s your thought on this? Thanks. 🙂

Corta87
Member
Corta87

Hello i have a question. I have an Samsung QLED TV with a 4k 120Hz panel and it is G-Sync compatible. I will play with fixed 60fps on 4k because my RTX 3080. What settings should i use?
120Hz on 4K, G-Sync and V-Sync i think both should be enabled.
What Framelimit should i set? 117FPS or 57 or can it still be on 60? Im am not sure about that.
Thank you for this great article.

Florian
Member
Florian

sorry i still don’t understand

why recommends Nvidea
V sync let the 3D setting decide, and not on?

first I use Gsync+Vsync + framelimiter

If Reflex is available in the game, should I turn off LLM in the Control Panel?

For example if I play a game that is very GPU bound and there is no reflex should I set LLM to ultra or on when using gsync + vsync + frame limiter .

Thank you so much.

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