What Is G-SYNC And What Does It Do?

G-SYNC synchronizes refresh rates of a monitor (Hz) to the frame rates of a GPU (FPS) in order to eliminate screen tearing and stuttering.

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What Is G Sync

Answer:

Gaming monitors with NVIDIA’s G-SYNC technology feature a dedicated module that provides a variable refresh rate for tear-free gameplay with compatible graphics cards.

Wondering what a G-SYNC monitor is and how it’s different from G-SYNC Compatible, G-SYNC Ultimate, or FreeSync displays? You’ve come to the right place!

What Is G-SYNC?

G-SYNC is a special chip installed inside a G-SYNC monitor that replaces the traditional scaler. It provides you with a variable refresh rate (VRR) and variable overdrive if you have a compatible graphics card.

There are three generations of G-SYNC modules:

  • v1 module with DisplayPort 1.2
  • v1 module with DisplayPort 1.2 and HDMI 1.4
  • v2 module with DisplayPort 1.4 (with DSC), HDMI 2.0, and a cooling fan (some newer modules may feature two or more HDMI 2.0 ports)
NVIDIA G-SYNC Module

How Does G-SYNC Work?

G-SYNC allows your monitor’s refresh rate (Hz) to change dynamically, according to your GPU’s frame rate (FPS). As a result, all screen tearing is eliminated up to the monitor’s maximum refresh rate at no noticeable (~1ms) input lag penalty.

So, if you have a 144Hz gaming monitor and you have 60FPS in a game, G-SYNC will dynamically change the display’s refresh rate to 60Hz in order to provide you with 60 whole frames per second without tearing.

Meanwhile, variable overdrive will ensure that the pixel response time speed is adjusted accordingly, thus preventing pixel overshoot at low FPS and ghosting at high frame rates.

Another advantage of the G-SYNC module is that it replaces the regular scaler in the monitor, so you’ll have a slightly lower input lag.

The main disadvantage is the price, as well as limited connectivity options since G-SYNC modules don’t have VGA, DVI, or USB-C (for DisplayPort Alt Mode) ports.

Picture-in-Picture and Picture-by-Picture modes are also not supported on G-SYNC monitors.

Since the regular scaler is replaced, older G-SYNC monitors don’t support display scaling, though modern graphics cards handle GPU scaling with no added lag, so this won’t be an issue for most users.

Some newer models support display scaling, but fiddling with CRU is required to make the option appear in the NVIDIA control panel.

G-SYNC vs FreeSync & G-SYNC Compatible

G Sync Module

Unlike G-SYNC, FreeSync and G-SYNC Compatible monitors don’t have dedicated modules.

Instead, they rely on VESA’s free and open-standard Adaptive-Sync protocols in DisplayPort and/or HDMI connectors for a variable refresh rate.

A G-SYNC Compatible monitor is essentially a FreeSync or ‘Adaptive-Sync’ monitor that’s been validated by NVIDIA to work without any issues when using their compatible cards.

So, what exactly makes G-SYNC special?

To start with, G-SYNC monitors usually have a wider VRR range than FreeSync and G-SYNC Compatible displays.

For instance, a 144Hz G-SYNC gaming monitor has a VRR range of 30-144Hz, whereas a similar FreeSync monitor will usually have a dynamic range of 48-144Hz.

So, if your frame rate were to drop to 40FPS, a G-SYNC monitor would change its refresh rate to 40Hz, while a FreeSync monitor would have to resort to LFC (Low Framerate Compensation) and multiply its refresh rate to 120Hz (40FPS x 3) in order to prevent tearing.

Triggering LFC causes minor stuttering, so the overall gaming experience will be more pleasant on a G-SYNC monitor in this case.

As previously mentioned, since the G-SYNC module replaces the regular scaler of the monitor, G-SYNC monitors have lower input lag, though most FreeSync monitors have imperceptibly low input lag anyway.

The upsides of not having a G-SYNC module include a lower price tag and more extensive connectivity options.

So, is G-SYNC worth it?

Well, it depends on the monitor and its FreeSync/G-SYNC Compatible counterpart, if it exists.

Sometimes, a FreeSync monitor will have just as wide VRR range as a G-SYNC model, and even though it may not have variable overdrive, its overdrive implementation can be very good nonetheless.

We have a dedicated article where we compare popular G-SYNC monitors to their FreeSync counterparts, as well as the best G-SYNC monitor buyer’s guide, which consists of all G-SYNC gaming monitors worth considering.

G-SYNC Ultimate

Gaming monitors with the G-SYNC Ultimate certification also feature a dedicated module, but with added HDR (High Dynamic Range) support.

The criteria for this certification have changed over time, however.

Here are the old requirements:

G SYNC Ultimate Old Requirements

And here you can see the current requirements for G-SYNC Ultimate:

G SYNC Ultimate Requirements

So, the very first G-SYNC Ultimate gaming monitors, such as the Acer X35 and the ASUS PG27UQ, offered a next-level HDR viewing experience thanks to their high 1000-nit peak brightness and multi-zone backlight (with full-array local dimming).

Nowadays, you can see G-SYNC Ultimate monitors with a lower 600-nit peak brightness and inferior multi-zone backlights – down to 32 edge-lit local dimming zones, for instance, from something like the 512-zone FALD solution of the Acer X35.

These monitors still offer somewhat decent (but not proper) HDR image quality, usually with VESA’s DisplayHDR 600 certification.

You get noticeably better HDR image quality in comparison to SDR or DisplayHDR 400, but you’re not getting the ‘true’ HDR viewing experience, more like a glimpse of it. Some scenes will look a lot better, others might even look worse than SDR.

In other words, G-SYNC Ultimate no longer guarantees amazing HDR image quality. It is as misleading as the other HDR certifications.

For the best HDR image quality, you’ll have to check if the monitor has a good full-array local dimming solution with many zones (or simply an OLED panel) among its specifications.

Note that G-SYNC Ultimate was previously branded as ‘G-SYNC HDR.’

G-SYNC Requirements

In order to use G-SYNC, you will need a G-SYNC monitor and a compatible NVIDIA graphics card (GTX 650 Ti Boost or newer) connected via DisplayPort.

Now, newer G-SYNC monitors, such as the Dell AW2721D, the LG 38GL950G, and the Acer XB273X, also allow G-SYNC to be used with AMD graphics cards over DisplayPort, and also offer HDMI-VRR for consoles via HDMI 2.1.

For G-SYNC Ultimate, you’ll need a GTX 1050 or newer graphics card with DisplayPort 1.4.

You can use our G-SYNC monitor list to find all G-SYNC and G-SYNC Ultimate monitors available.

All monitors certified by NVIDIA as ‘G-SYNC Compatible’ can be found in the list at the bottom of the article.

NVIDIA ULMB & ULMB 2

Some (not all) G-SYNC monitors are also paired with NVIDIA’s ULMB (Ultra Low Motion Blur) technology, which uses backlight strobing to reduce perceived motion blur at the cost of picture brightness.

Note that ULMB and G-SYNC can’t be active at the same time – unlike some other MBR (Motion Blur Reduction) implementations, such as ELMB-Sync by ASUS or Aim Stabilizer Sync by Gigabyte, which allow for simultaneous backlight strobing and VRR (FreeSync or G-SYNC Compatible) performance.

The new ULMB 2 certification guarantees exceptional backlight strobing performance by ensuring that the monitor meets the following requirements:

  • Backlight strobing is supported at the monitor’s maximum refresh rate
  • At least 250-nits of brightness
  • Effective motion clarity of > 1000Hz (i.e. a refresh rate of at least 250Hz)
  • Minimal strobe crosstalk

ULMB 2 still doesn’t support simultaneous performance with VRR, but it brings vertical-dependent overdrive, which allows for different overdrive levels to be applied at different parts of the screen.

Overdrive is tuned differently for normal operation and backlight strobing, therefore, the pixel response time can be pushed further with ULMB 2 enabled as overshoot can be hidden (the period when the backlight is turned off).

ULMB 2 monitors:

NVIDIA Reflex Analyzer

Further, several G-SYNC monitors feature the NVIDIA Reflex Analyzer tool, which allows you to measure the latency between the supported monitor and a compatible mouse.

Compatible NVIDIA Reflex Analyzer monitors include:

  • Acer Predator X34S
  • Acer Predator X38S
  • Acer Predator XB273U NX
  • AOG AGON PRO AG274QG
  • ASUS ROG Swift PG279QM
  • ASUS ROG Swift PG259QNR
  • AOC AGON PRO AG254FG
  • MSI Oculux NXG253R
  • Acer Predator X25
  • Acer Predator X28
  • Dell Alienware AW2521H
  • Dell Alienware AW2524H
  • Lenovo Y25G-30
  • LG 25GR75FG
  • ViewSonic XG251G
  • ViewSonic XG271QG
  • ViewSonic XG321UG
  • ASUS PG27AQN
  • Acer XB273UF
  • AOC AG276QSG
  • ASUS PG248QP

Click here to check out the list of all compatible NVIDIA Reflex Analyzer mice and video games.

Finally, keep in mind that NVIDIA Reflex Analyzer and NVIDIA Reflex are two different things.

NVIDIA Reflex doesn’t measure input lag, but rather reduces it in supported games.

To take advantage of it, you’ll need an NVIDIA GTX 900-series or newer graphics card and to enable the Reflex option in the settings of a compatible game, some of which include:

  • Fortnite
  • Valorant
  • Apex Legends
  • Call of Duty: Black Ops Cold War
  • Call of Duty: Modern Warfare
  • Call of Duty: Warzone
  • Destiny 2

NVIDIA G-SYNC Pulsar

At CES 2024, NVIDIA announced the G-SYNC Pulsar technology.

In short, it combines the VRR performance of a native G-SYNC monitor with ULMB backlight strobing in order to reduce perceived motion blur while simultaneously keeping screen tearing at stuttering at bay.

At the moment, simultaneous VRR and MBR performance is possible on some displays without the native G-SYNC module via Gigabyte’s Aim Stabilizer Sync, ASUS’ ELMB-SYNC and similar implementations. However, the actual performance is mostly lackluster due to strobe crosstalk and similar visual artifacts.

For now, there are three G-SYNC Pulsar displays announced, including the ASUS ROG Swift PG27AQNR, the Acer Predator XB273U F5 and the AOC AGON PRO AG276QSG2, all based on the same 27″ 1440p 360Hz IPS panel, likely with DisplayHDR 600 support.

Instead of being on a proprietary G-SYNC module, NVIDIA teamed up with MediaTek to develop a new scaler that will feature upgraded connectivity options, including DP 1.4 and HDMI 2.1, as well as passive cooling instead of a dedicated fan.

The scaler will feature G-SYNC Pulsar, VRR and Reflex Analyzer support for NVIDIA GPUs, whereas Intel and AMD graphics cards will only be able to utilize VRR.

Given the huge backlight strobing performance improvement NVIDIA’s ULMB2 brings and the fact that a native G-SYNC module ensures stable VRR performance, we’re optimistic about G-SYNC Pulsar and hope to finally see proper VRR + MBR performance.

Cloud G-SYNC

G SYNC Now VRR Support

In 2024, NVIDIA also added variable refresh rate support to its G-SYNC Now cloud gaming service. It requires an NVIDIA GPU (16-series / 20-series or newer) and a monitor with variable refresh rate support (G-SYNC, G-SYNC Compatible, FreeSync or HDMI 2.1 VRR).

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Rob Shafer

Rob is a software engineer with a Bachelor’s degree from the University of Denver. He now works full-time managing DisplayNinja while coding his own projects on the side.