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.



3072 Comments For “G-SYNC 101”

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HopelessNinersFan
Member
HopelessNinersFan

Hi!

Thank you for the guide, it’s definitely made life much easier for me. I do have some confusion though. I have a 4080 SUPER, 32 GB RAM, i9 13980HX, and 240 HZ display – I’m quite proud of it. It mentions to enable Reflex if available or Low-Latency mode if FPS doesn’t always exceed the refresh rate, but how does that fit with setting a FPS limiter to limit the FPS regardless? I apologize in-advance if I’m misinterpreting, I’m still relatively new to PC gaming on a more advanced level. Furthermore, is Reflex even worth it if my 4080 isn’t ever anywhere near getting pinned? I heard Reflex only has an impact if your GPU is at 99%. Thanks again!

Regards,

Herconomicon
Member
Herconomicon

Do you recommend v-sync set to ON globally or per application ?

Vizima
Member
Vizima

So, I’ve been doing a lot of testing over the past few weeks. My PC specs are: Intel Core i7-13700k and my monitor is an Asus 240Hz OLED. First off, I want to thank you for the guide, it started my hyperfocus of testing a lot stuff xD. I stumbled upon something peculiar while playing Apex Legends.

When I cap my framerate (I use RTSS for this) and enable both G-Sync and V-Sync in the NVIDIA Control Panel, and then select Reflex in-game, my framerate gets capped at 225, as the guide suggests. It feels incredibly smooth, but I noticed something strange – I could NOT bunny hop anymore (on controller). Turning off V-Sync allows me to bunny hop again, but I dislike the drop in smoothness, so I decided to try some other options.

The first thing I tried was disabling Reflex altogether. Despite expecting Reflex to reduce input delay, its absence actually allowed me to bunny hop again (which I consider an indicator of low input delay). Then, I decided to re-enable everything – G-Sync, V-Sync in NCP, and Reflex in-game – and capped my framerate in RTSS to 200. To my surprise, I found that I could bunny hop once again, experiencing low input delay and maintaining very smooth gameplay. Can anyone explain what’s happening here? Because with the exact same settings at 225, I couldn’t achieve the same result.

Here are my MSI Afterburner benchmark results while playing in-game:

200 FPS (capped in RTSS)
Average FPS: 198
1% Low FPS: 185
0.1% Low FPS: 166

Thanks a lot!

toby23
Member
toby23

If I have a 120 Hz monitor with G-Sync and can achieve 115fps average in a game, is there any negative to locking the framerate to 59fps with RTSS to lower power consumption and smooth out Frametime?
Running unlocked in MSFS results in the Frametime jumping around all over the place but locking to 59 fps makes it steady.

PS Super article, thank you so much for keeping it updated.

Ryan Le
Member
Ryan Le

In Sea of Thieves, I have V-Sync turned off, but there is also an option to set the buffering to either double or triple, and there’s no off option. I set it to double buffering, but do I still need to enable V-Sync in NVCP? Would the in-game double buffering option (with in-game V-Sync off) conflict with NVCP V-Sync since it’s also running on double buffering?

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