G-SYNC 101: External FPS Limiter HOWTO


In-game vs. External Framerate Limiters

As described in G-SYNC 101: In-game vs. External FPS Limiters, 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 lag; how much depends on the limiter and its implementation.

In-game framerate limiters, however, 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 with G-SYNC to prevent V-SYNC-level input lag instead.

RTSS is a CPU-level FPS limiter, and introduces up to 1 frame of delay, whereas Nvidia Inspector uses a driver-level FPS limiter, which introduces 2 or more frames of delay. See G-SYNC 101: In-game vs. External FPS Limiters for complete details, along with input latency tests comparing the two external solutions against an in-game limiter.

RivaTuner Statistic Server: <1 Frame Delay

RTSS is available standalone here, or bundled with MSI Afterburner here.

If only a framerate limiter is required, the standalone download will suffice. MSI Afterburner itself is an excellent overclocking tool that can be used in conjunction with RTSS to inject an in-game overlay with multiple customizable performance readouts.

Blur Buster's G-SYNC 101: External FPS Limiter HOWTO

RTSS can limit the framerate either globally or per profile. To add a profile, click the “Add” button in the lower left corner of the RTSS windows and navigate to the exe. To set a frame limit, click the “Framerate limit” box and input a number.

Nvidia Inspector: 2> Frame Delay

An unofficial extension of the official Nvidia Control Panel, Nvidia Inspector (download here) exposes many useful options the official control panel does not, including a driver-level framerate limiter.

Nvidia Inspector can limit the framerate either globally or per profile (more details on profile creation can be found here).

To set a frame limit, locate the “Frame Rate Limiter” dropdown in the “2 – Sync and Refresh” section, select the desired limit, and then click the “Apply Changes” button in the upper right corner of the Nvidia Inspector window.

Blur Buster's G-SYNC 101: External FPS Limiter HOWTO

As of Nvidia Profile Inspector version 2.1.3.6 and Nvidia driver branch R381 or later, a new “Frame Rate Limiter Mode” dropdown has been introduced with a “Limiter V2 – Force Off” option:

Blur Buster's G-SYNC 101: External FPS Limiter HOWTO

This option claims to reduce the limiter’s input lag; exactly by how much, and with what combination of settings, remains to be determined.



220 Comments For “G-SYNC 101”

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gen36
Member
gen36

Hi, I have a question about limiting frame rate at (refresh rate – 3).

My understanding is that if FPS > refresh rate, GSYNC defaults to VSYNC behavior (if VSYNC is enabled in Nvidia CP), which can result in additional input lag.

But I have some confusion on this. Example scenario:

– 144 Hz monitor.
– I’m playing an undemanding game, VSYNC OFF, and get 200 FPS.
– I turn on GSYNC + VSYNC, and get 144 FPS.
– With GSYNC + VSYNC on, is it defaulting to VSYNC ON behavior? Frame rate is not exceeding refresh rate but *would have* if vsync was off.

(My confusion is coming from the section in the FAQ saying if your frame rate exceeds refresh rate, to cap at a value lower than refresh rate, but if vsync is on, FPS doesn’t exceed refresh rate anyway)

Silver3
Member
Silver3

I was wondering if you could explain me a very persistent Frametime-Spiking-relating issue I’ve got recently with the console-emulator Cemu that I am tearing my hair out about at this time.

[… original comment modified here for length; view below comment reply for pertinent details w/follow-up…]

Sorry btw for that wall of text, but I am quite at my wit’s end by now on my way comprehending other/similar builds’ success although they probably don’t care half of that, pc-related, the way I do and I seemingly checked all of your mentioned points possibly causing frametime-spikes
and will continue with the hardware-part tomorrow.
If you have any suggestion that merely could hint in a direction I overlooked, PLEASE let me know.

Thank you for reading.

Skwuruhl
Member
Skwuruhl

On the topic of FPS limiters: Two tests have been done somewhat recently that found that RTSS provides more consistent frame times than in-game limiters do (at the expense of 1 frame of input lag)
https://youtu.be/xsXFUVYPIx4
https://www.reddit.com/r/Competitiveoverwatch/comments/9vcxz5/rtss_vs_ingame_fps_cap_or_frame_limit/
What’s your take on these?

rpate124
Member
rpate124

What value should the frame time limit be set to in rtss?

GITS_2501
Member
GITS_2501

Amazingly detailed, thanks for the guide. Is there a difference between having V-SYNC: ON versus VSYNC: Fast?

Thanks heaps.

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