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60 Hz Panels, SLI, Surround, And Availability

G-Sync Technology Preview: Quite Literally A Game Changer
By , Chris Angelini

Going Faster: Is This Tech Limited To High-Refresh Panels?

You'll notice that the first G-Sync-enabled monitor already supports a very high refresh rate (well beyond the technology's sweet spot) and a 1920x1080 resolution. But Asus' display has its own limitations, like a six-bit TN panel. We wanted to know whether Nvidia plans to limit G-Sync to high-refresh rate displays, or if we'd see it used on more common 60 Hz monitors. Also, the enthusiast in us wants access to 2560x1440 as soon as possible.

Nvidia reiterated for us G-Sync is best experienced when you're pushing your graphics card to frame rates between 30 and 60. As a result, the technology can really benefit conventional 60 Hz screens retrofitted with the G-Sync module.

So why start with 144 Hz? It sounds like a lot of the display vendors want to enable low motion blur functionality (3D LightBoost), which does require high refresh rates. But for those who're willing to leave that feature out (and why not, since it's not compatible with G-Sync right now anyway), it's possible to build a G-Sync-enabled panel for a lot less money.

As far as resolutions go, it sounds like QHD screens at refresh rates as high as 120 Hz will start showing up some time early next year.

Are There Any Issues Between SLI And G-Sync?

Nvidia's G-Sync FAQ clearly states that G-Sync is compatible with SLI; the graphics card attached to the display is the one that manages the variable refresh technology. 

Now, the complete story requires a little more explanation. We've spent plenty of time discussing AMD and its frame pacing technology added to the Catalyst driver suite. Nvidia handles this through logic built into the Kepler architecture. The company says it'll be in Maxwell and beyond of course, but we're pretty sure we heard about it even prior to Kepler. At any rate, the same pacing technology that keeps frames displayed consistently with V-sync off in SLI is what you need for G-Sync to function properly. There's no additional work that needs to be done. Those frames are displayed from the "master" GPU, which also controls G-Sync.

What Does It Take To See G-Sync In Surround?

Now, obviously, the idea of slinging multiple cards together to output to a 1080p screen doesn't sound very necessary. Even a mid-range Kepler-based card should manage the frame rates needed to make that resolution playable. But it's also not possible to run a two-card SLI configuration with three G-Sync-capable displays in Surround, either.

This is a limitation of the current display outputs on Nvidia's cards, which typically include two DVI ports, HDMI, and a DisplayPort connector. G-Sync requires DisplayPort 1.2, and an adapter won't work (neither will an MST hub). The only way to make Surround happen is with three cards, each attached to its own monitor. Of course, we presume that there's nothing stopping Nvidia's partners from coming out with a "G-Sync Edition" card sporting more DP connectivity.

G-Sync And Triple Buffering

Would you need triple-buffering enabled to get smooth performance out of G-Sync, similar to what you'd do with V-sync-on? The answer is no, not only does G-Sync not require triple-buffering because the pipeline is never stalled, but the use of triple buffering in G-Sync is detrimental; it adds an additional frame of latency with no performance benefit. Unfortunately, this is often set by games, so there's no way to manually override it.

What About Games That Typically Don't Respond Well To V-sync-Off?

Games like Skyrim, part of our usual benchmark suite, are intended to be run with V-sync enabled on a 60 Hz panel (although this drives some of us nuts due to the impact of input lag). Testing them requires modifying certain .ini files. So how does G-Sync behave with titles based on the Gamebryo and Creation engines, which are sensitive to V-sync settings? Does it cap out at 60 FPS?

That's a characteristic of the game, and G-Sync doesn't change it, just like running on a 120 or 144 Hz display with V-sync enabled wouldn't. Nvidia says that games like Skyrim should work fine with its technology, though, so long as they're limited to the frame rates the engine expects. In those cases, set your refresh to 60 Hz, turn on G-Sync, and the feature will conform to the correct maximum frame rate.

When Will This Stuff Be Available, And For How Much?

Currently, Nvidia expects its OEM partners to start shipping G-Sync-enabled displays in the first quarter of next year. The company says cost will be less of an issue than perhaps many enthusiasts expect, since the G-Sync module replaces the monitor's scaler. The pricing delta between those two components is the difference you'll see. 

Hope You Have A Fast Mouse

As a final note, Nvidia makes it a special point to mention that you're best off with a fast mouse should you shift over to a G-Sync-based setup. A polling rate of 1000 Hz will help ensure your input device doesn't negatively affect reaction times.

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