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.



2845 Comments For “G-SYNC 101”

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xwqqchc
Member
xwqqchc

Hi thanks for the guide. Slightly specific question but 1) When using G-Sync+NVCP V-Sync, no reflex, no LLM and no FPS cap in any program my FPS is still capped at my monitors refresh rate (280hz, stable 280fps). Is this thanks to V-Sync by itself? And would this be causing higher input latency as opposed to using reflex etc?

2) Tangentially, in CS2 I see much higher frametime variance when using G-Sync+NVCP V-Sync+Reflex/or LLM Ultra and the FPS is capped by either of those options (~260fps, stable). Yet if I disable Reflex/ LLM Ultra, with no FPS cap in game – my fps will still remain capped (~280fps, stable) yet the frametime variance will disappear. If I then cap the FPS in game, or in any program (with Reflex/LLM still off) at 280fps myself, the variance returns. Do you know what might be going on here?

Sorry for the hyper-specific question, I’m mostly concerned if there is potentially added delay but again thank you for the guide.

am1kam
Member
am1kam

Hello, im still confused on what is the “Most” Optimal setting for G-Sync
is it the following?

NVCP Settings:
G-Sync Enabled (Fullscreen Only)
Preferred refresh rate to Highest Available
Ultra Low Latency Enabled or (If Reflex is available use it On+Boost)
Frame Limiter enabled ( 138 FPS CAP)
V-Sync On

Ingame Settings:
Everything related to V-Sync is disabled
No FPS Cap

Few more questions
1: Would using RTSS be better than Nvidia’s Frame Limiter
2: Would Low Latency Mode be better on “On” instead of Ultra w/ the Frame Limiter Enabled
3: Why is V-Sync enabled through NVCP instead of the game?

crazyhelmet
Member
crazyhelmet

what is the latency difference between “gsync on + nvcp vsync on + ingame limiter” and “gsync on + nvcp vsync on + reflex on or ultra”

Swavemantrey
Member
Swavemantrey

Hey bro, thanks everything is smooth as intended . But quick question. What about Triple buffering? it says it helps when Vsync is also enabled. should i have this disabled or enabled ?

sundboy5220
Member
sundboy5220

Hello friend
Did I follow the guidelines correctly?
Can you give me setting suggestions?
CPU: 7800X3D
GPU: RTX4070

LCD: PG259QNR (360Hz)
Nvidia
G-Sync: Enable
V-Sync:Adaptation
Low Latency Mode:On

Game(Valorant)
Reflex: OFF
FPS limiter: 356

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