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G-SYNC 101: Control Panel

Published Jun 20, 2017 by in: G-SYNC

G-SYNC Module

The G-SYNC module is a small chip that replaces the display’s standard internal scaler, and contains enough onboard memory to hold and process a single frame at a time.

The module exploits the vertical blanking interval (the span between the previous and next frame scan) to manipulate the display’s internal timings; performing G2G (gray to gray) overdrive calculations to prevent ghosting, and synchronizing the display’s refresh rate to the GPU’s render rate to eliminate tearing, along with the delayed frame delivery and adjoining stutter caused by traditional syncing methods.

G-SYNC Demo

The below Blur Busters Test UFO motion test pattern uses motion interpolation techniques to simulate the seamless framerate transitions G-SYNC provides within the refresh rate, when directly compared to standalone V-SYNC.

G-SYNC Activation

“Enable for full screen mode” (exclusive fullscreen functionality only) will automatically engage when a supported display is connected to the GPU. If G-SYNC behavior is suspect or non-functioning, untick the “Enable G-SYNC, G-SYNC Compatible” box, apply, re-tick, and apply.

Blur Buster's G-SYNC 101: Control Panel

G-SYNC Windowed Mode

“Enable for windowed and full screen mode” allows G-SYNC support for windowed and borderless windowed mode. This option was introduced in a 2015 driver update, and by manipulating the DWM (Desktop Windows Manager) framebuffer, enables G-SYNC’s VRR (variable refresh rate) to synchronize to the focused window’s render rate; unfocused windows remain at the desktop’s fixed refresh rate until focused on.

G-SYNC only functions on one window at a time, and thus any unfocused window that contains moving content will appear to stutter or slow down, a reason why a variety of non-gaming applications (popular web browsers among them) include predefined Nvidia profiles that disable G-SYNC support.

Note: this setting may require a game or system restart after application; the “G-SYNC Indicator” (Nvidia Control Panel > Display > G-SYNC Indicator) can be enabled to verify it is working as intended.

G-SYNC Preferred Refresh Rate

“Highest available” automatically engages when G-SYNC is enabled, and overrides the in-game refresh rate selector (if present), defaulting to the highest supported refresh rate of the display. This is useful for games that don’t include a selector, and ensures the display’s native refresh rate is utilized.

“Application-controlled” adheres to the desktop’s current refresh rate, or defers control to games that contain a refresh rate selector.

Note: this setting only applies to games being run in exclusive fullscreen mode. For games being run in borderless or windowed mode, the desktop dictates the refresh rate.

G-SYNC & V-SYNC

G-SYNC (GPU Synchronization) works on the same principle as double buffer V-SYNC; buffer A begins to render frame A, and upon completion, scans it to the display. Meanwhile, as buffer A finishes scanning its first frame, buffer B begins to render frame B, and upon completion, scans it to the display, repeat.

The primary difference between G-SYNC and V-SYNC is the method in which rendered frames are synchronized. With V-SYNC, the GPU’s render rate is synchronized to the fixed refresh rate of the display. With G-SYNC, the display’s VRR (variable refresh rate) is synchronized to the GPU’s render rate.

Upon its release, G-SYNC’s ability to fall back on fixed refresh rate V-SYNC behavior when exceeding the maximum refresh rate of the display was built-in and non-optional. A 2015 driver update later exposed the option.

This update led to recurring confusion, creating a misconception that G-SYNC and V-SYNC are entirely separate options. However, with G-SYNC enabled, the “Vertical sync” option in the control panel no longer acts as V-SYNC, and actually dictates whether, one, the G-SYNC module compensates for frametime variances output by the system (which prevents tearing at all times. G-SYNC + V-SYNC “Off” disables this behavior; see G-SYNC 101: Range), and two, whether G-SYNC falls back on fixed refresh rate V-SYNC behavior; if V-SYNC is “On,” G-SYNC will revert to V-SYNC behavior above its range, if V-SYNC is “Off,” G-SYNC will disable above its range, and tearing will begin display wide.

Within its range, G-SYNC is the only syncing method active, no matter the V-SYNC “On” or “Off” setting.

Currently, when G-SYNC is enabled, the control panel’s “Vertical sync” entry is automatically engaged to “Use the 3D application setting,” which defers V-SYNC fallback behavior and frametime compensation control to the in-game V-SYNC option. This can be manually overridden by changing the “Vertical sync” entry in the control panel to “Off,” “On,” or “Fast.”

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3709 Comments For “G-SYNC 101”

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Halfwit
Member
Halfwit

Excellent article, really well done!

I do have a question, though: if you just wanted to test the general input lag of the monitor, what settings would you use? Or, let’s break it down like this, as I’m equally interested to hear your opinion on all of these:

1. Would you use a game to test it (CS:GO, for example) or would you test it in Windows desktop?

2. Would you go for the crosshair method or the movement method?

3. What framerate and refresh rate would you set your monitor to, assuming it’s a 144 Hz G-Sync monitor?

Thanks in advance for your input!

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8 years 2 months ago
jorimt
Author
jorimt

Unfortunately, since the high speed camera/led method measures the entire button-to-pixel input lag chain at once, it’s difficult to isolate the display lag from everything else.

You’d have to use a different method, such as the methods TFTCentral or other monitor review sites use.

Good news is, G-SYNC monitors in general are very low lag, usually <10ms for the 100Hz variety, and <5ms for the 144Hz and up panels.

That said, the Chief Blur Buster knows more about these other methods than I, and should be able to answer your question in more detail, so feel free to start a thread in the input lag sub forum:
http://forums.blurbusters.com/viewforum.php?f=10

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8 years 2 months ago
Halfwit
Member
Halfwit

Thank you, I’ll give that a try!

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8 years 2 months ago
Zanthra
Member
Zanthra

What interests me about Fast Sync is how it looks to the game. In general, when a video game is running it’s render loop, V-Sync (with or without G-Sync) will synchronously or asynchronously block the rendering of the next frame from starting until after the GPU discards the front buffer. Limiting the framerate with an in-game setting does something very similar, just using an internal clock between renders instead of using the GPU’s clock.

The thing about Fast Sync is that it presents itself as a non-blocking rendering pipeline, just as V-Sync off does. The GPU immediately gives it a free buffer to render to, allowing it to incorporate the latest data into that frame. If the game renders multiple frames in between vertical refreshes, the first ones are discarded to make room for the next frame to be rendered, and the GPU takes the latest complete frame for display on the next refresh.

Because of this, I think that Fast Sync can be seen as an alternative in many cases to limiting the FPS, especially on older games or low refresh rate displays where the game can get to multiples of the refresh rate, or games that don’t have an in-game FPS limit (since you can avoid the added latency of RTSS).

Ideally, there would be a extra low latency FPS Limit mode designed into games to go along with adaptive refresh rate solutions, where they use a feedback system like a PID to insert the waiting period (if the framerate is above the limit) before collecting the data to render the frame, based on an estimate of how long it will take to render the next frame.

The great benefit is that the adaptive refresh rate solves the problem of near misses if the estimated render time is off. If the frame is 1ms late, the monitor will simply wait for the frame to be complete and scan it out immediately when it is ready. If it’s 1ms early, the GPU will wait for the Vertical Sync. Either way, you get a minimum amount of time that any frame is finished rendering and not being displayed, where new input data cannot be integrated.

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8 years 4 months ago
jorimt
Author
jorimt

Yes, while it is moot point if you are using G-SYNC (in any configuration), Fast Sync does have its uses, and is effectively a global way to enable “true” triple buffer V-SYNC in almost any game. And as you say (regardless of the microstutter), it can suffice as an FPS limiter in place of an external limiter, reducing latency AND eliminate tearing all at once.

That said, in-game limiters have thankfully made a return as of late (Frostbite and UE4 engines, Overwatch, and even games like Watch Dogs 2 and Dishonored 2, admittedly limited to presets; 60 FPS, 120 FPS, etc), but I’d like to see one in every major game myself, as it is invaluable for G-SYNC and FreeSync technology. And in-game limiters, much like Fast Sync, can also utilize lower frametimes to deliver frames faster.

Eventually, I’d even like to see an external predictive FPS limiter with little to no latency, but we know that would be difficult to achieve.

G-SYNC, FreeSync, Fast Sync, in-game limiters, external limiters; the more options the better I say.

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8 years 4 months ago
Perdition
Member
Perdition

So in Overwatch, optimal settings for the least amount of input lag would be:

In-game frame target of 3 less than max refresh rate (in my case 162fps)
G-sync On in NVCP in Full Screen Mode
V-sync set to “Use 3D Application” and disabled in Overwatch Menu

Correct?

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8 years 4 months ago
Perdition
Member
Perdition

I reread the article and it appears I should have V sync On in NVCP and not on in game. However, I don’t quite fully understand the reasoning behind it.

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8 years 4 months ago
jorimt
Author
jorimt

Those settings are correct but for “Vertical sync,” which you want set to “On” in the Nvidia Control Panel (not “Use the 3D application setting”; you will get partial tearing with this, even with G-SYNC enabled), and V-SYNC disabled in-game (this goes for any game).

As for NVCP V-SYNC vs. in-game V-SYNC, read my “Nvidia Control Panel V-SYNC vs. In-game V-SYNC” just two sections above “Conclusion” in this article. It explains the reasoning for that aspect pretty clearly.

If you need further clarification, I will attempt to offer it, but my article is already very clear on why you need G-SYNC + V-SYNC to avoid tearing; I would simply be repeating myself in any follow-up answer on this.

Be sure to read the G-SYNC 101: Range entry of this article for more details on G-SYNC + V-SYNC “Off” vs. G-SYNC + V-SYNC “On,” if you haven’t already. Refer to the Range chart there as well.

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8 years 4 months ago
MichaelJamesJohnson
Member
MichaelJamesJohnson

Optimal G-Sync Settings

Can you add a section for OS settings?

Did I understand correctly that you recommend turning off full screen optimizations and game mode?

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8 years 4 months ago
jorimt
Author
jorimt

@MichaelJamesJohnson

I don’t have any specific OS settings to recommend; what exists in the “Optimal G-SYNC Settings” is it.

As for the Windows 10 Creators update’s “Game Mode,” and “fullscreen optimizations,” they were disabled for this specific testing to ensure a proper control environment.

For the record, I don’t disapprove of the “Game Mode,” and “fullscreen optimization” settings, and you can use them in whatever configuration you wish. They are simply too new, and too little is known about their effects to trust, so I disabled them to be safe.

I did, however, do some brief off-the-record tests of the Game Mode, Game bar, and fullscreen optimization settings, and posted my findings here:
http://forums.blurbusters.com/viewtopic.php?f=5&t=3073&start=260#p26491

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8 years 4 months ago
Bishi
Member
Bishi

Game mode is worth turning off for all but the weakest PCs. Decent PCs literally get nothing out of it.

Like1Vote Down 
8 years 4 months ago
Bishi
Member
Bishi

Great writeup, thanks guys!

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8 years 4 months ago
jorimt
Author
jorimt

Happy to provide it Bishi! We are looking to publish more articles on the subject of input lag in the near future.

Stay tuned…

Like2Vote Down 
8 years 4 months ago
wpDiscuz

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