Last week, we published the hardware spec for Microsoft's next Xbox - Project Scorpio. However, there was one little detail we held back, an aspect of the new console we didn't want to get lost in the noise. In the here and now its applications will be limited, but in the fullness of time, it may help to bring about a profound shift in how displays interface with games hardware. To cut a long story short, Scorpio supports AMD's FreeSync - and the upcoming variable refresh rate support baked into the next-gen HDMI 2.1 spec.
So what's the big deal here? In an ideal world, every single console game would run at 60fps, perfectly sychronised with the refresh rate of the attached display. This would result in a super-smooth, low latency gameplay experience - something you can see in the here and now in titles including the Forza Motorsport series and Halo 5. However, if a game targets 60fps and doesn't consistently hit the target, the experience is compromised in one of two ways.
First of all, if the game runs with v-sync enabled, frames are dropped and this introduces noticeable judder - what's happening here is that the game only has a small window in which to synchronise with the screen. If a frame renders over its 1/60th of a second budget, the GPU stalls, waiting for the next refresh. Alternatively, the developer may simply decide to drop synchronisation with the screen - when this happens, highly intrusive, ugly screen-tearing kicks in.
Adaptive refresh technology like AMD's FreeSync completely eliminates tearing and reduces stutter significantly by allowing the GPU to trigger the display refresh instead of adhering to a hard and fast 60Hz cycle. Essentially, the screen produces the next image immediately after the GPU finishes rendering it. The technology was pioneered by Nvidia's G-Sync, but it's the open standard variants - FreeSync and the upcoming HDMI 2.1 implementation - that Scorpio aims to support. In fact, Microsoft has actually implemented the FreeSync 2 standard, meaning compatibility with HDR and full support across the range of potential frame-rates. Paired with a supported screen, this will even eliminate tearing on games running with adaptive v-sync with frame-rates under 30fps, something not supported on most FreeSync 1 screens (VRR range varied on a per-screen basis, with 40Hz to 60Hz commonplace).
Actually showing what VRR (variable refresh rate) technology can do is very difficult - it's unlikely you're reading this on an adaptive sync screen, and even if you are, video player software doesn't support it. However, we thought we'd try simulating a comparison. In the video demo below, we show the difference between VRR, v-sync on and v-sync off by locking Nvidia's G-Sync Pendulum demo to 40fps, and capturing it at 60Hz with the standard modes. This easily highlights v-sync judder and the tearing artefacts you get when you disable v-sync - exactly as it was designed to. To simulate VRR, we configured our capture device to grab footage at native 40Hz, then ran all three captures at 25 per cent speed. This provides a common denominator in terms of refresh that works with a standard screen and clearly shows the artefacts of the existing modes, along with the consistency of VRR.
So in the short term, what does this mean for prospective Project Scorpio buyers? How do you get to experience the new tech? Well, until the HDMI 2.1 standard is ratified, there are no living room displays that are VRR-enabled. To see the benefit, you'll need to have a PC monitor - a 4K one preferably, though 1080p screens will work - and it needs to support FreeSync over HDMI. This limits the amount of potential screens as it's more frequently run via DisplayPort, a video output that is not supported by Scorpio. Looking forward, a 4K HDR monitor with FreeSync 2 support really is the best way to ensure optimal results from this feature. In here and now, what we can say is that Scorpio's adaptive sync support is baked in at the system level - the developer doesn't need to worry about it (though they could enable higher frame-rate caps for VRR users if the overhead is there). And on top of that, it works across all Xbox content that runs on the new console - Xbox 360 back-compat titles and Xbox One games.
But it's the longer term outlook that is arguably more important. There's a reason why games target either 60fps or 30fps: both divide equally into the 60Hz output of a traditional screen, meaning a smooth, consistent update. With the display refresh put in the developer's hands, arbitrary performance targets like 40fps or 45fps could be targeted. We've tested both on PC using a G-Sync screen running games with Riva Tuner Statistics Server's frame-rate cap in place and both of these frame-rates look so much better than the console standard 30fps. With games that target 60fps, performance drops down to around 50fps are really difficult to pick up on owing to the lack of tearing and reduced v-sync judder.
Of course, reaching the point where VRR is specifically targeted by developers will probably take years, but the point is that take-up from manufacturers - especially in living room displays - is going to require a mainstream piece of gaming technology to drive adoption. We've already talked about how Scorpio pushes console hardware to the next level, and we wanted to isolate FreeSync and VRR support and showcase it as an example of just how much attention to detail is going into the next Xbox. There's no real need for Microsoft to support this, but the fact that it is - and that the most hardcore gamers will appreciate it - illustrates just how much the focus has changed at Xbox HQ. And of course, the chances are that if one console vendor pushes ahead with supporting the tech, the competition will follow.
Closer to Scorpio's release, we'll be testing the FreeSync support, perhaps coming up with a screen recommendation or two.
We learned about Project Scorpio's variable refresh features at an exclusive briefing at Xbox HQ. Microsoft paid for travel and accommodation.