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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  • LordOfTheBoired - Wednesday, January 8, 2014 - link

    It still exists because DVI(and consequently, HDMI) requires it to exist. That's not the only anachronism DVI requires.

    And while it's definitely a dinosaur and completely irrelevant, it's not really for the reasons you think.
    It's being used nowadays as the time between the completion of displaying one frame and the beginning of displaying the next. Which isn't really WRONG, but... much like the concept of vertical sync, it's an archaic function that's directly tied to CRT functionality.

    The vertical blanking interval has nothing to do with blanking the SCREEN. The name comes because during VBlank your CRT's driver hardware cuts off the electron beam while it travels from the bottom-right corner back to the top-left, so you don't leave a big slash across your screen. Anything drawn during the vertical blanking interval is... blanked out.
    And at the end of the VBlank period, your graphics controller generates the VSync pulse to turn the beam back on. And at the same time it sends the VSync interrupt so your software know it's time to start drawing again. And they better drop whatever they're doing and start drawing RIGHT NOW, because the beam waits for neither man nor code.

    Yes, there's actually two different VSyncs. And yes the entire concept is backwards for the modern world.
    And it still exists because DVI was designed for easy interoperability with VGA, and HDMI is more or less a clone of DVI. So it explicitly calls for VBlank and HBlank periods, and sync signals at the end of them. And thus we're generating VSync, VBlank, HSync, HBlank, and even the actual scan across the individual lines in an era where no displays work that way, because our display CONNECTIONS require them.
    So the graphics card must generate all of this ancestral baggage, and the display must scrape it all off and throw it away to reconstruct the image, because DVI is a clunky hack.
    If we were handling digital video SANELY, we'd never generate any of that crap(and DisplayPort doesn't!).
  • pierrot - Tuesday, January 7, 2014 - link

    I wonder if NVIDIA will backpedal on G-Sync now and implement this with software, I hope so because I like free - they could then leave the G-Sync for the xxxtreme gamerz
  • Rontalk - Tuesday, January 7, 2014 - link

    Mantle, freesync all very good staff and free. What Nvidia gives us for free?
  • Gigaplex - Tuesday, January 7, 2014 - link

    Free? You have to buy the hardware.
  • bill5 - Wednesday, January 8, 2014 - link

    The nvidia sticker on the side is worth $100's to most fanboys LOL. That is what Nvidia gives you free, the .01 cents sticker. Makes their card automatically worth $200 more than the AMD equivalent that performs the same.
  • mathew7 - Tuesday, January 7, 2014 - link

    This is just a hack. Clearly AMD wants to play catch-up. Gaming on a laptop screen is ridiculous.
    Don't get me wrong.....I'm using AMD triple-Eyefinity setup and would love it....on the desktop. But who said nVidia could not do the same on laptops? They just went further.
  • tcube - Tuesday, January 7, 2014 - link

    that's the catch... anybody can do it... on any panel(laptop desktop possibly even tv's)... apparently the only thing is panel builders need to update their firmwares to correctly handle this (again) since modern screens don't actually need this functionality.
  • LordOfTheBoired - Wednesday, January 8, 2014 - link

    You missed the point.
    It's not that you can do this on a laptop(which I'm sure can be done with GSync). It's that there are displays in the wild that work with FreeSync RIGHT NOW.

    And not just top-end displays. This one's apparently a 1366x768 panel in a 600-dollar laptop, which is HARDLY premium gear.
    I desperately want to know what OTHER panels are quietly supporting VESA variable VBlank and just waiting for someone to throw the switch. It's possible that once AMD enables it in the public drivers, your three-monitor setup CAN use FreeSync/VVVB.
    THAT'S what makes this interesting. Not that AMD demonstrated a competitor to GSync, but that they demonstrated it with pre-existing hardware and a pre-existing standard.
  • Fergy - Tuesday, January 7, 2014 - link

    Would FreeSync work for DVI, HDMI and Displayport? Why does Nvidia need 3 memory chips in the monitor? Does AMD use video memory for this? Wouldn't it be smarter to let the monitor buffer the last frame? Would letting the GPU buffer the last frame give less latency?
  • tcube - Tuesday, January 7, 2014 - link

    Most possibly the framebuffer, as huge as the modern day framebuffers are keeping a simple frame in memory is quite nothing really. Even a 4K frame is some 16MB in size... so compare that to any modern GPU that has upwards of 1GB.

    I think this approach is more error prone then the G-synch approach which in turn I think is a massive overkill... So possibly G-synch will be for Extreme Gamers and FreeSynch for everybody else. No idea if the screen firmware can be updated via DVI/HDMI/VGA etc but if it could that would be a huge trick to pull... Imagine a driver update that would turn your screen into a FreeSynch one with a simple driver update... well... one is entitled to his dreams isn't he?

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