Adaptive-Sync added to DisplayPort spec


— 1:10 PM on May 12, 2014

PC gaming animation may soon become more fluid than ever, thanks to a development just announced by the folks at the VESA display standards organization. VESA has officially added a feature called Adaptive-Sync to the DisplayPort 1.2a specification, which means that a G-Sync-style adaptive refresh mechanism could be built into nearly every new desktop monitor in the coming months and years.

The press release explains exactly what's at stake:

NEWARK, CA (12 May 2014) — The Video Electronics Standards Association (VESA®) today announced the addition of Adaptive-Sync to its popular DisplayPort 1.2a video interface standard. This technology delivers several important capabilities to computer users: Adaptive-Sync provides smoother, tear-free images for gaming and judder-free video playback. It also significantly reduces power consumption for static desktop content and low frame rate video.

Computer monitors normally refresh their displays at a fixed frame rate. In gaming applications, a computer's CPU or GPU output frame rate will vary according to the rendering complexity of the image. If a display's refresh rate and a computer's render rate are not synchronized, visual artifacts—tearing or stuttering—can be seen by the user. DisplayPort Adaptive-Sync enables the display to dynamically match a GPU's rendering rate, on a frame-by-frame basis, to produce a smoother, low latency, gaming experience.

We saw a demo from AMD of such technology in use on a laptop back at CES, which AMD cheekily dubbed "FreeSync," since the tech didn't require a cost-adding G-Sync module in order to work. That feature, however, only exists in select laptop displays, where adaptive sync exists primarily for power-saving reasons. With today's announcement, variable refresh tech becomes part of the spec for external displays, as well, and gets its new name: 

Adaptive-Sync is a proven and widely adopted technology. The technology has been a standard component of VESA's embedded DisplayPort (eDP) specification since its initial rollout in 2009. As a result, Adaptive-Sync technology is already incorporated into many of the building block components for displays that rely on eDP for internal video signaling. Newly introduced to the DisplayPort 1.2a specification for external displays, this technology is now formally known as DisplayPort Adaptive-Sync.

The approval of this spec is only one step in a long process before we can expect to see desktop monitors that support Adaptive-Sync on store shelves. The makers of display scaler and control chips still have work to do, and those companies have been rather sluggish in developing ASICs capable of supporting 4K resolutions at 60Hz. (That's why a lot of the early 4K displays use dual tiles, which is way less than optimal.) 

Still, I think this announcement has to count as a victory for AMD's "FreeSync" initiative, its counter to Nvidia's G-Sync push. In fact, the VESA release quotes an AMD engineer espousing the benefits of Adaptive-Sync: 

DisplayPort Adaptive-Sync enables a new approach in display refresh technology, said Syed Athar Hussain, Display Domain Architect, AMD and VESA Board Vice Chairman. Instead of updating a monitor at a constant rate, Adaptive-Sync enables technologies that match the display update rate to the user's content, enabling power efficient transport over the display link and a fluid, low-latency visual experience.

The fact that a spec update happened is also a bit of a blow to Nvidia, simply because the firm's G-Sync guru, Tom Petersen, told us at CES that he didn't think an update to DisplayPort was needed for variable refresh. Evidently, VESA was persuaded otherwise.

The addition of Adaptive-Sync does mean Nvidia has achieved its stated goal of pushing the industry forward on this front. Yet it also means Nvidia's window of exclusivity, where only G-Sync-compatible displays combined with GeForce graphics cards will offer variable refresh tech, could be fairly narrow. That window had already shrunk somewhat with rumored last-minute changes to the G-Sync module. Issues with the module are apparently responsible, at least in part, for the fact that G-Sync-compatible monitors haven't yet reached the market as anticipated.

Variable refresh technologies like Adaptive-Sync offer potential benefits beyond added smoothness in gaming. For video playback, display refresh rates could be lowered to sync with low-frame-rate video sources like 24 FPS movies, eliminating the need for inverse telecine conversion. For less intensive desktop workloads where the screen contents are often static, variable refresh tech could allow "the display refresh rate to be reduced seamlessly, lowering system power and extending battery life," according to VESA.

Update: AMD has provided us with a series of questions and answers that clarifies the relationship between its own Project FreeSync initiative and VESA's Adaptive-Sync feature, as well as offering some insights about when we can expect to see Adaptive-Sync-ready displays. Here are the juiciest bits:

Q: How are DisplayPort™ Adaptive-Sync and Project FreeSync different?
A: DisplayPort™ Adaptive-Sync is an ingredient DisplayPort™ feature that enables real-time adjustment of monitor refresh rates required by technologies like Project FreeSync. Project FreeSync is a unique AMD hardware/software solution that utilizes DisplayPort™ Adaptive-Sync protocols to enable user-facing benefits: smooth, tearing-free and low-latency gameplay and video.

Q: When can I buy a monitor compatible with Project FreeSync?
A: AMD has undertaken every necessary effort to enable Project FreeSync in the display ecosystem. Monitor vendors are now integrating the DisplayPort™ Adaptive-Sync specification and productizing compatible displays. AMD is working closely with these vendors to bring products to market, and we expect compatible monitors within 6-12 months.

Q: What is the supported range of refresh rates with FreeSync and DisplayPort™ Adaptive-Sync?
A: AMD Radeon™ graphics cards will support a wide variety of dynamic refresh ranges with Project FreeSync. Using DisplayPort™ Adaptive-Sync, the graphics card can detect and set an appropriate maximum and minimum refresh rate based on the capabilities reported by the display. Potential ranges include 36-240Hz, 21-144Hz, 17-120Hz and 9-60Hz.

Q: What AMD Radeon™ GPUs are compatible with Project FreeSync?
A: The first discrete GPUs compatible with Project FreeSync are the AMD Radeon™ R9 290X, R9 290, R7 260X and R7 260 graphics cards. Project FreeSync is also compatible with AMD APUs codenamed “Kabini,” “Temash,” “Beema,” and “Mullins.” All compatible products must be connected via DisplayPort™ to a display that supports DisplayPort™ Adaptive-Sync.

I think there are a few big-ticket takeways from AMD's statement.

First, there's the time frame of six to 12 months before Adaptive-Sync displays become available. That's pretty wide latitude, and we're talking about the first wave of compatible monitors. A year could pass before Adaptive-Sync displays ship to consumers (or longer if that estimate is off.) Assuming Nvidia and its partners get their G-Sync hardware working soon, the window for G-Sync exclusivity could still be fairly broad.

Second, I'm happy to see that the ranges of refresh rates possible with Adaptive-Sync displays is so wide and extends to relatively low numbers. The early G-Sync hardware we tested didn't go quite as low, and Nvidia was clearly missing some of the benefit of this tech in performance-limited scenarios, where the user can feel its impact the most. I do expect production G-Sync modules to lower the refresh limit, too, although that's nothing I've confirmed with certainty.

Finally, it's clear VESA's effort and AMD's Project FreeSync are not to be confused. Nvidia, Intel, and other GPU makers participate in standards bodies like VESA and are likely to support DisplayPort 1.2a with Adaptive-Sync, as well.

   
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