G-SYNC 101: Range


Blur Buster's G-SYNC 101: Range Chart

Exceeds G-SYNC Range

G-SYNC + V-SYNC “Off”:
G-SYNC disengages, tearing begins display wide, no frame delay is added.

G-SYNC + V-SYNC “On”:
G-SYNC reverts to V-SYNC behavior when it can no longer adjust the refresh rate to the framerate, 2-6 frames (typically 2 frames; approximately an additional 33.2ms @60 Hz, 20ms @100 Hz, 13.8ms @144 Hz, etc) of delay is added as rendered frames begin to over-queue in both buffers, ultimately delaying their appearance on-screen.

G-SYNC + Fast Sync*:
G-SYNC disengages, Fast Sync engages, 0-1 frame of delay is added**.
*Fast Sync is best used with framerates in excess of 2x to 3x that of the display’s maximum refresh rate, as its third buffer selects from the “best” frame to display as the final render; the higher the sample rate, the better it functions. Do note, even at its most optimal, Fast Sync introduces uneven frame pacing, which can manifest as recurring microstutter.
**Refresh rate/framerate ratio dependent (see G-SYNC 101: G-SYNC vs. Fast Sync).

Within G-SYNC Range

Refer to “Upper & Lower Frametime Variances” section below…

Upper & Lower Frametime Variances

G-SYNC + V-SYNC “Off”:
The tearing inside the G-SYNC range with V-SYNC “Off” is caused by sudden frametime variances output by the system, which will vary in severity and frequency depending on both the efficiency of the given game engine, and the system’s ability (or inability) to deliver consistent frametimes.

G-SYNC + V-SYNC “Off” disables the G-SYNC module’s ability to compensate for sudden frametime variances, meaning, instead of aligning the next frame scan to the next scanout (the process that physically draws each frame, pixel by pixel, left to right, top to bottom on-screen), G-SYNC + V-SYNC “Off” will opt to start the next frame scan in the current scanout instead. This results in simultaneous delivery of more than one frame in a single scanout (tearing).

In the Upper FPS range, tearing will be limited to the bottom of the display. In the Lower FPS range (<36) where frametime spikes can occur (see What are Frametime Spikes?), full tearing will begin.

Without frametime compensation, G-SYNC functionality with V-SYNC “Off” is effectively “Adaptive G-SYNC,” and should be avoided for a tear-free experience (see G-SYNC 101: Optimal Settings & Conclusion).

G-SYNC + V-SYNC “On”:
This is how G-SYNC was originally intended to function. Unlike G-SYNC + V-SYNC “Off,” G-SYNC + V-SYNC “On” allows the G-SYNC module to compensate for sudden frametime variances by adhering to the scanout, which ensures the affected frame scan will complete in the current scanout before the next frame scan and scanout begin. This eliminates tearing within the G-SYNC range, in spite of the frametime variances encountered.

Frametime compensation with V-SYNC “On” is performed during the vertical blanking interval (the span between the previous and next frame scan), and, as such, does not delay single frame delivery within the G-SYNC range and is recommended for a tear-free experience (see G-SYNC 101: Optimal Settings & Conclusion).

G-SYNC + Fast Sync:
Upper FPS range: Fast Sync may engage, 1/2 to 1 frame of delay is added.
Lower FPS range: see “V-SYNC ‘On'” above.

What are Frametime Spikes?

Frametime spikes are an abrupt interruption of frames output by the system, and on a capable setup running an efficient game engine, typically occur due to loading screens, shader compilation, background asset streaming, auto saves, network activity, and/or the triggering of a script or physics system, but can also be exacerbated by an incapable setup, inefficient game engine, poor netcode, low RAM/VRAM and page file over usage, misconfigured (or limited game support for) SLI setups, faulty drivers, specific or excess background processes, in-game overlay or input device conflicts, or a combination of them all.

Not to be confused with other performance issues, like framerate slowdown or V-SYNC-induced stutter, frametime spikes manifest as the occasional hitch or pause, and usually last for mere micro to milliseconds at a time (seconds, in the worst of cases), plummeting the framerate to as low as the single digits, and concurrently raising the frametime to upwards of 1000ms before re-normalizing.

G-SYNC eliminates traditional V-SYNC stutter caused below the maximum refresh rate by repeated frames from delayed frame delivery, but frametime spikes still affect G-SYNC, since it can only mirror what the system is outputting. As such, when G-SYNC has nothing new to sync to for a frame or frames at a time, it must repeat the previous frame(s) until the system resumes new frame(s) output, which results in the visible interruption observed as stutter.

The more efficient the game engine, and the more capable the system running it, the less frametime spikes there are (and the shorter they last), but no setup can fully avoid their occurrence.

Minimum Refresh Range

Once the framerate reaches the approximate 36 and below mark, the G-SYNC module begins inserting duplicate refreshes per frame to maintain the panel’s minimum physical refresh rate, keep the display active, and smooth motion perception. If the framerate is at 36, the refresh rate will double to 72 Hz, at 18 frames, it will triple to 54 Hz, and so on. This behavior will continue down to 1 frame per second.

Regardless of the reported framerate and variable refresh rate of the display, the scanout speed will always be a match to the display’s current maximum refresh rate; 16.6ms @60Hz, 10ms @100 Hz, 6.9ms @144 Hz, and so on. G-SYNC’s ability to detach framerate and refresh rate from the scanout speed can have benefits such as faster frame delivery and reduced input lag on high refresh rate displays at lower fixed framerates (see G-SYNC 101: Hidden Benefits of High Refresh Rate G-SYNC).



2981 Comments For “G-SYNC 101”

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wrdh
Member
wrdh

Hey! I hope you can help me. My PC setup includes an RTX 4070 (ASUS TUF OC), i5-14600KF, and an ASUS TUF VG27AQA1A monitor (supports FreeSync and is G-Sync compatible). My problem is that games don’t feel smooth, even though the FPS shows 144-170 (currently using DisplayPort, 165Hz), with FreeSync turned on and G-Sync for fullscreen games also turned on. When I use G-Sync, my monitor flickers (only in fullscreen games).

Here’s a summary of the settings:

V-Sync is on
LLM – Ultra
G-Sync is on
I’ve had this problem since I bought my new PC a month ago. I don’t think games should look like this, so I suspect a driver update might help when a new version comes out.

Thank you for your time!

kizx
Member
kizx

hey πŸ˜€ , quick question was gives the less latency between RTTS to cap frame or NVCP? thanks

jtcuth48
Member
jtcuth48

Hey Jorimt! Apologies if this has been asked before.

If the game does not have customizable vsync settings and it’s forced on (mainly looking at the From Software games here), is enabling vsync in the control panel still optimal? Will in-game vsync on and the control panel vsync conflict and create any adverse effects? Should I let the 3D application decide in this case?

Thanks!

kizx
Member
kizx

Hello Jorimt, I have a question for the longest time I have like weird feels bad/ stuttering /frame drops idk how to call it in my league of legends game due to dual monitor my primary being 140 hz and my secondary being not the same 60 hz. After reading your post about imput-lag I managed to isolate to problem by going full screen with G-sync-V-sync on in the nvidia control panel but then I keep reading you also mention that if the game we are playing doesnt allow to set a custom value for fps we must do it with RTTS or insane nvidia so I did 141 inside Nvidia. My question is do I need to change it to 141 even if I have the V-Sync on from nvidia or not? But then I kept on reading and also tried the low latency mode on and ultra. From my testing ( very hard to tell the difference ) I think ON gives me the lowest latency and I think ultra gives me the best Hz, frames stability of every animations but overall I do feel like I have more latency having V-sync then not having it. capping my fps at 141 in Nvidia control panel with G-Sync and low latency ultra or ON do seem to feel like im at lower latency with no tearing but its not as perfect than if I had V-Sync on…

What should I do to have the best of both worlds : low latency feeling smooth but also no hz monitor/frames issues.

Thank you.

finaltidus
Member
finaltidus

Hi Jorimt! Glad to see that you are still active here. Sorry I have some very noob questions on my recent weird observations on certain games which I play.

I have recently upgraded my monitor and graphics card to a G-Sync compatible 4k 144hz Dell G3223Q and RTX 4070. My CPU is i5-8600K so I understand that I may experience moderate to severe CPU bottlenecking. On the latest Nvdia 551.52 driver.

My current settings on NVCP are as follows with my target as having the lowest input lag following your optimal settings article.

G-Sync – ON
V-Sync – On
LLM – Ultra

All of my games stay way below the 144fps threshold without any fps limiter. The G-sync range for this monitor is 48-144hz.

Recently I play this game Robocop- Rogue City. There is no Reflex support on this game. With the above settings, my fps is around 60-70fps but with MAJOR stutters until it’s almost unplayable. It cannot be my CPU bottleneck as the CPU is around 40% utilisation. My GPU also ranges from 80-90% utilisation.

I was trying frantically to try to resolve this stutter problem but to no avail. Then for the fun of it, I just set LLM to off and tried out the game. Guess what? No stutters and GPU utlisation went to 99% most of the time. My FPS went to around 80-90fps and very smooth!

I tried to set LLM to Ultra and Off again to ensure that this wasn’t a one off event. But no. LLM Ultra=stutterfest while Off=smooth

Any reason why this is happening? Should I then set LLM as Off for my case in all games going forward for games that DO NOT support Reflex?

In my other games that have Reflex, I set it as On+Boost as default and so far no problems with it.

I understand that Reflex will override LLM regardless of the setting in NVCP.

What then should be the optimal settings in my current specs and objective in achieving lowest input lag, tear free experience and minimal stutter? I am not keen on trying every single game I have and having to tinker with the settings all the time as I have 100+ games on my PC so I would appreciate a general guide to an optimal settings.

Thank you so much!!! πŸ™‚

Thxt
Member
Thxt

Turn LLM on “ON” or “OFF”. You can find it https://blurbusters.com/gsync/gsync101-input-lag-tests-and-settings/8/. I think in ur case you want to set LMM to “ON”, just check the link i sent for jorimt’s answer.

finaltidus
Member
finaltidus

Thanks!!

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