Nvidia's G-Sync goes mobile, adds features

Variable refresh comes to laptops and windowed games

In addition to introducing the GeForce GTX 980 Ti today, Nvidia is making some updates to its G-Sync variable display refresh technology. Among the changes, the biggest news is the introduction of a mobile version of G-Sync for use in gaming laptops with mobile GeForce graphics chips.

G-Sync hits the road
The mobile version of G-Sync is distinct from the desktop version because laptops typically allow the GPU to connect to the display's control logic directly, without a display scaler chip standing in the way. As a result, Nvidia has managed to implement the mobile version of G-Sync without the custom module used in desktop displays. Instead, the GPU directly controls the display's behavior.

According to Nvidia's Tom Petersen, the plan going forward is for all GeForce-equipped laptops to ship with G-Sync support as a standard feature.

At least four different laptop makers will introduce G-Sync-capable laptops this week at the Computex trade show in Taipei, including Gigabyte, MSI, Asus, and Clevo, as indicated above. Gigabyte's offerings even include SLI multi-GPU mojo.

Many of these laptops have LCD panels with 75Hz peak refresh rates, and Nvidia promises they will be "gamer grade" displays. I got the chance to see a couple of these systems in action briefly, and they do indeed appear to provide the same sort of silky smooth animation that we've come to expect from desktop displays with variable-refresh technology.

Petersen assured us that we can expect "the same behaviors" out of mobile G-Sync displays that we've come to expect from their desktop counterparts, including the collision-avoidance logic in low-FPS scenarios and custom overdrive behavior to prevent ghosting. Since the G-Sync module isn't present, the GPU and driver software will combine to make sure these features work correctly.  In fact, a GPU shader program will assist with LCD overdrive compensation, which Petersen told us is a "small amount of work for the GPU." Nonetheless, he claimed that the initial tuning of each LCD panel for the proper overdrive behavior in a variable-refresh setting is "a non-trivial effort," one for which Nvidia will continue to assume responsibility under the G-Sync banner.

More desktop displays, too
In addition to expanding to laptops, G-Sync will be coming to a wider variety of desktop displays soon, many of which are likely to be announced or at least shown in some form this week at Computex. Nvidia provided us with the following list of upcoming monitors from just two manufacturers, Asus and Acer.

The most exciting prospects here may be the trio of IPS offerings from Asus, including the PG279Q, which has the deadly combo of a 2560x1440 resolution, a 144Hz refresh rate, and an IPS-type panel. Then again, Acer already has the XB270HU in the market with the same basic attributes.

Acer's X34 is mighty intriguing; this curved 34" display has a near-4K resolution on an IPS panel with a 75Hz refresh rate. I need a trio of those things arrayed on my desktop for some Project Cars action as soon as possible.

I'm also fascinated by the two 27" IPS displays listed with 4K native resolutions. Those monitors could be the do-everything upgrade enthusiasts can embrace. Acer's 35" VA panel has the potential to offer a nice mix of quality and affordability, as well.

I expect to learn more about some of these monitors as the week progresses, and hopefully we'll be able to get our mitts on some of them for review soon.

Better behaviors, more control
Owners of G-Sync-capable systems can expect some upgrades in Nvidia's latest graphics drivers, too.

Most notably, the firm is adding support for variable display refresh rates on the Windows desktop, so that users can run games in windowed mode and still experience smoother animation. Making this mode work with variable refresh rates is a pretty nice trick, since the Desktop Window Manager application is natively a fixed-refresh application that composites the results from multiple windows.  Nvidia's software guys managed to make it work by having the DWM's refresh track with the refresh rate of the currently in-focus window. In Petersen's words, "we are the driver, so we can do things behind the scenes."

Petersen tells us G-Sync should work with games running in both windowed and borderless windowed mode. That fact should be popular with a lot of gamers, especially those who like to stream to Twitch or the like.

Nvidia is also taking a page from AMD's FreeSync by adding the ability to disable variable refresh synchronization (vsync) when the frame rate from the graphics card ventures beyond the range of refresh intervals supported by the display. This option is available in Nvidia's latest 352.90 drivers, which we used in our GeForce GTX 980 Ti review. See the screenshot above.

Unlike AMD, though, Nvidia will not let go of synchronization when frame rates drop below the monitor's tolerance.  Instead, Nvidia's implementation will only allow tearing when the frame rate exceeds the speed of the display. Doing so makes sense, I think, given the collision-avoidance logic Nvidia has built for low-refresh scenarios; it tends to handle that situation pretty well. Allowing tearing at really high frame rates should make games more responsive by letting the game loop execute as quickly as possible. Folks playing twitch shooters should appreciate this option.

One of the better kept secrets of G-Sync displays is the presence of an ultra-low motion blur (ULMB) mode on some monitors. This mode sacrifices variable refresh, but it promises greater clarity through the use of backlight strobing. I looked at it right here in my review of the Asus PG278Q, if you're curious. Some folks really appreciate the benefits of this mode, and Nvidia has decided to raise its profile by including it as an option in its driver control panel alongside G-Sync variable refresh. The monitor I had connected for the screenshot above doesn't support ULMB, so the menu option is unfortunately not shown there. Still, this little refinement is a welcome one.

Tags: Graphics Displays

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