AMD has been relatively silent on the topic of NVIDIA’s variable refresh rate G-Sync technology since its announcement last year. At this year’s CES however, AMD gave me a short demo of its version of the technology.

Using two Toshiba Satellite Click notebooks purchased at retail, without any hardware modifications, AMD demonstrated variable refresh rate technology. According to AMD, there’s been a push to bring variable refresh rate display panels to mobile for a while now in hopes of reducing power consumption (refreshing a display before new content is available wastes power, sort of the same reason we have panel self refresh displays). There’s apparently already a VESA standard for controlling VBLANK intervals. The GPU’s display engine needs to support it, as do the panel and display hardware itself. If all of the components support this spec however, then you can get what appears to be the equivalent of G-Sync without any extra hardware.

In the case of the Toshiba Satellite Click, the panel already supports variable VBLANK. AMD’s display engines have supported variable VBLANK for a couple of generations, and that extends all the way down to APUs. The Satellite Click in question uses AMD’s low cost Kabini APU, which already has the requisite hardware to support variable VBLANK and thus variable display refresh rates (Kaveri as well as AMD's latest GPUs should support it as well). AMD simply needed driver support for controlling VBLANK timing, which is present in the latest Catalyst drivers. AMD hasn’t yet exposed any of the controls to end users, but all of the pieces in this demo are ready and already available.

The next step was to write a little demo app that could show it working. In the video below both systems have V-Sync enabled, but the machine on the right is taking advantage of variable VBLANK intervals. Just like I did in our G-Sync review, I took a 720p60 video of both screens and slowed it down to make it easier to see the stuttering you get with V-Sync On when your content has a variable frame rate. AMD doesn’t want to charge for this technology since it’s already a part of a spec that it has implemented (and shouldn’t require a hardware change to those panels that support the spec), hence the current working name “FreeSync”.

AMD’s demo isn’t quite as nice as NVIDIA’s swinging pendulum, and we obviously weren’t able to test anywhere near as many scenarios, but this one is a good starting point. The system on the left is limited to 30 fps given the heavy workload and v-sync being on, while the system on the right is able to vary its frame rate and synchronize presenting each frame to the display's refresh rate. AMD isn’t ready to productize this nor does it have a public go to market strategy, but my guess is we’ll see more panel vendors encouraged to include support for variable VBLANK and perhaps an eventual AMD driver update that enables control over this function.

In our review I was pretty pleased with G-Sync. I’d be even more pleased if all panels/systems supported it. AMD’s “FreeSync” seems like a step in that direction (and a sensible one too that doesn’t require any additional hardware). If variable VBLANK control is indeed integrated into all modern AMD GPUs, that means the Xbox One and PS4 should also have support for this. Given G-Sync’s sweet spot at between 40 - 60 fps, I feel like “FreeSync” would be a big win for AMD’s APUs.

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  • rscsrAT - Monday, January 6, 2014 - link

    with Desktops, power usage doesn't matter, as long as everything stays quiet. And if no one knows about this technology and advantages, no one would be able to spend additional money and development on anything.
  • Frenetic Pony - Monday, January 6, 2014 - link

    There's a ton of "Great stuff" that software guys want which the hardware guys don't do. Software is only indirectly related to hardware purchase so far as hardware companies are concerned. So anytime a software guy emails with "hey do this!" they kind of just ignore it for a good while.
  • jasonelmore - Tuesday, January 14, 2014 - link

    If it was that easy, Nvidia would be doing it that way. Some form of DRAM is needed with fast I/O to the panel with super low latency.

    Now in a notebook, it's easy to put the dram on the laptop's motherboard. Apple has been requesting at least a small amount of Dram on panels for years to store the framebuffer for power savings. The same dram can be used for gsync.

    There is definately a lot of varibles unknown with AMD's solution, but they have yet to show a demonstration that equals Nvidia's 60 FPS thru 144 FPS Gsync.
  • efeman - Monday, January 6, 2014 - link

    In either case, the panel manufacturer needs to provide support for it, correct? This is probably an easier target, as it doesn't need a separate board like G-Sync does.
  • TheJian - Tuesday, January 7, 2014 - link

    Gsync doesn't require a separate board, unless replacing in an older model. You will see NEW models come with it inside replacing the current scalers that are already in there. What do you think they take out when they mod the current one? A board or at least some chip...But only because they are using it to retrofit an model that came before the tech did. Even if they leave it in, you won't need it in the future, you will included the gsync setup instead.
  • yelped - Monday, January 6, 2014 - link

    Sounds good...
  • Gunbuster - Monday, January 6, 2014 - link

    So they have had the ability in hardware for years but it takes Nvidia making a product for them to derp along and figure that out? I'm sure this works great just like Enduro, and Crossfire frame pacing.
  • blanarahul - Monday, January 6, 2014 - link

    +1. I do hope that they don't screw this up.
  • SikSlayer - Monday, January 6, 2014 - link

    Yeah truly. This barebones demo says to me they just slapped this together to say that they can do it too. Not that there was much to G-Sync technically. good to see it though.
  • purehg - Monday, January 6, 2014 - link

    I don't think this is equivalent to GSync. GSync works by making the monitor board holding VBLANK until GPU sends an image. FreeSync uses a VESA standard to change VBI speculatively depends on what the driver thinks the next VBLANK should be. There is software overhead first, and it won't work for the most important frames, when the framerate fluctuates, so you will still see tearing and stutter occasionally. If the app runs in constant frame, like how AMD's demo is doing, then the driver should be able to speculate properly and get the correct VBLANK configured. With the pendulum demo NVIDIA has however, since the framerate can fluctuate, FreeSync won't work nearly as well.

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