Inside the next Xbox: Project Scorpio tech revealed

Last week, Digital Foundry was invited to Microsoft’s Redmond campus for an exclusive preview of the technology in the next Xbox, codenamed Project Scorpio. As specs reveals go, this one is unprecedented: it’s a first in terms of early access to key system architects, and one of a kind in terms of timing. Scorpio is seemingly running ahead of schedule, to the point where we’re likely six months away from release at least, and we’ve already seen impressive software running beautifully on production silicon.

There’ll be all the specs you’ll need in this piece, but the reason Microsoft flew us out to talk to those involved was straightforward: the numbers, as impressive as they are, don’t fully represent what the final product aims to deliver. Nor can the number of compute units and teraflops represent the passion the Xbox team has injected into this project. Microsoft has a point to prove. It’s not just about performance, it’s about pushing the quality of console design to a new level – in all areas.

The headlines? Combining smart design with sheer horsepower, Project Scorpio hits the six-teraflop target set for it as E3 last year, thanks to a custom GPU that has been designed from the ground up for optimal performance on today’s game engines – and that runs at an unprecedentedly high clock speed for a console. The GPU is paired with 12GB of fast GDDR5 memory and a custom eight-core CPU, and the whole thing is housed in a compact body with integrated power supply and, for a console, state-of-the-art cooling.

Performance is remarkable. We saw a Forza Motorsport demo running on the machine at native 4K and Xbox One equivalent settings, and it hit 60 frames per second with a substantial performance overhead – suggesting Scorpio will hit its native 4K target across a range of content, with power to spare to spend on other visual improvements. And while 4K is the target, Microsoft is paying attention to 1080p users, promising that all modes will be available to them.

The push for 4K and the Scorpio Engine

In Redmond, the pitch comes thick and fast before the tech deep dive kicks off. The overall outline of Project Scorpio has evolved since Phil Spencer presented it at last year’s E3, and in some key respects it sounds familiar to the PlayStation 4 Pro’s proposition – a point not lost on Microsoft. 4K ultra HD visuals to suit the new generation of televisions are clearly the target, but Microsoft’s solution means substantial spec upgrades over the Pro design in virtually all areas. That said, Sony’s philosophy of ‘smart’ GPU design is also in effect here, executed in a very different manner, and backed up with a lot more horsepower.

“To me, [4K] means a very specific set of things. It’s a lot more than delivering than those eight-million-plus pixels to the screen while playing games,” says Kevin Gammill, Group Program Director of the Xbox Core platform. “It’s about delivering those pixels with 4K assets, so they look great. It’s about delivering those pixels with HDR and wide colour gamut fidelity. It’s about delivering those pixels with no loss of frame-rate compared to the 1080p version of that title – that’s super-important to us. Spatial audio adds to the immersive experience as well: to truly land that gameplay experience, it’s not just about what you see, but what you hear.”

Core to the new console is the Scorpio Engine, the new SoC (system on chip) developed once again in conjunction with AMD. In common with many aspects of the box, engineering the new processor was based on a revolutionary workflow – one that could only really be achieved on a mid-generation refresh design.

Rich presents a final specs overview of Project Scorpio.

Project Scorpio Xbox One PS4 Pro
CPU Eight custom x86 cores clocked at 2.3GHz Eight custom Jaguar cores clocked at 1.75GHz Eight Jaguar cores clocked at 2.1GHz
GPU 40 customised compute units at 1172MHz 12 GCN compute units at 853MHz (Xbox One S: 914MHz) 36 improved GCN compute units at 911MHz
Memory Bandwidth 326GB/s DDR3: 68GB/s, ESRAM at max 204GB/s (Xbox One S: 219GB/s) 218GB/s
Hard Drive 1TB 2.5-inch 500GB/1TB/2TB 2.5-inch 1TB 2.5-inch
Optical Drive 4K UHD Blu-ray Blu-ray (Xbox One S: 4K UHD) Blu-ray

“As we landed on 4K, Andrew [Goossen] and team did a pretty deep analysis,” Gammill continues. “We have this developer tool called PIX [Performance Investigator for Xbox]. It lets us do some GPU trace capture. He and his team did a really deep analysis across a breadth of titles with the goal that any 900p or better title would be able to easily run at frame-rate at 4K on Scorpio. That was our big stake in the ground, and so with that we began our work speccing out what the Scorpio Engine is. It’s not a process of calling up AMD and saying I’ll take this part, this part and this part. A lot of really specific custom work went into this.”

Traditionally, games creators have to work to the characteristics of the console platform, but because Scorpio’s design brief was to scale up existing titles to 4K, the hardware team could profile actual, shipping games and customise the design to fit common characteristics. PIX provided the data that was then fed into a hardware emulator, where the Microsoft team could then see how those titles would run on prospective Scorpio hardware. Multiple configurations could be tested in order to get the best balance.

“What we did was to take PIX captures from all of our top developers… By hand we went through them and then extrapolated what the work involved would be for that game to support a 4K render resolution,” says Andrew Goossen, Technical Fellow, Graphics. “Now we had a model for all of our top-selling Xbox One games where we could tweak the configuration for the number of CUs, the clock, the memory bandwidth, the number of render back-ends, the number of shader engines, the cache size. We could tweak our design and figure out what was the most optimal configuration. It was incredibly valuable for us to be able to make those trade-offs, because ultimately these Xbox One titles are the ones that we… wanted to get up to 4K.”

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