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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  • Andromeduck - Tuesday, January 7, 2014 - link

    I think the difference is nvidia's is done in hardware where this is done through software

    from what I understand, in gsync refreshes the display when the next frame is received whereas in freesync frame time is set by the previous frame
  • bwat47 - Monday, January 6, 2014 - link

    Does anyone know which displays and which AMD gpu's support/will support this VBLANK variable? I currently have an amd 280x and an asus VG248QE
  • chowzilla - Monday, January 6, 2014 - link

    Per Anand, support has been in place for a couple generations. Since your 280X is current generation your GPU is good.

    Unfortunately I don't see any possibility of existing monitors getting support for this feature. In most cases there is no way for a user to upgrade the firmware (no USB interface, etc). On top of that, the marketing opportunities would further discourage vendors from bringing support to current monitors.
  • psychobriggsy - Tuesday, January 7, 2014 - link

    This is probably part of the reason for GSync - branding monitors that support it, and providing a monitor display controller that implements it (or something stupidly similar but proprietary). I presume that support for this feature is not provided in the monitor information data that the monitor sends to the computer, so you can't auto-detect monitor support to turn it on without the consumer needing specific knowledge. So maybe there's a risk of "Boom!" ...
  • Hairs_ - Monday, January 6, 2014 - link

    This is brilliant news, although as many people have said it exposes just how lazy our technology engineers can be. Failing to put in simple fixes which solve obvious problems at no cost with existing open standards, until someone forces them to. And I'm not having a go at AMD alone here, but also panel makers, PC makers, OEMs... ridiculous.
  • althaz - Monday, January 6, 2014 - link

    You're blaming the wrong people. It's not the engineers' fault, it's the corporate giants fault. They could have brought this technology out, but simply didn't see the value in it.

    There's value in it now for AMD by devaluing their competitor's investment in a proprietary technology.

    Corporations don't care about value to the consumer after all.
  • shabby - Monday, January 6, 2014 - link

    Why is the frame rate 29fps on the left and 49fps on the right?
  • zoob - Monday, January 6, 2014 - link

    It says right in the article why. VSYNC vs FreeSync.
  • Alexvrb - Monday, January 6, 2014 - link

    29.9x, you mean? AKA 30FPS? Traditional V-Sync on the left, FreeSync-enabled V-sync on the right. If you've got something running at ~50 FPS on a non-variable VBLANK 60hz panel, and you turn on regular ol' V-Sync, it runs at 30FPS. The panel on the right using FreeSync doesn't seem to suffer from the same limitations.

    Now, we can't be certain how fine-grained it is until we get a proper review, but at a minimum it's clearly a huge leap above what we've got now, without being limited to G-Sync capable hardware. This needs to be in every panel. Screw proprietary solutions, this could (and should) be supported by everyone.
  • 2bdkid - Monday, January 6, 2014 - link

    So our monitor must support VBLANK and we must be using AMD graphics, doubt Nvidia will do anything with this.

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