Leaked PDF sheds light on Microsoft's Project Scorpio, 4K gaming plans – ExtremeTech
Details on Microsoft’s Project Scorpio and how it might handle 4K gaming have been hard to come by ever since Microsoft announced the new platform. All we’ve known are a few basic specs, like the platform’s memory bandwidth (320GB/s), eight-core CPU, and available computational horsepower (6TFLOPS). Now we have more details thanks to a leaked PDF from a Microsoft developer website.
Eurogamer has the full details on the PDF, which doesn’t appear to be publicly available. According to Microsoft’s documentation, the Xbox Scorpio ditches the ESRAM cache the Xbox One relied on to deliver higher performance and acceptable frame rates. The PS4 and Xbox One are much more alike, architecturally speaking, than any previous pair of game consoles. ESRAM was one of the major differences between them — the Xbox One uses a 32MB ESRAM cache (divided into four 8MB blocks) to supplement its DDR3 memory interface, while the Sony PS4 has a unified 8GB GDDR5 memory pool.
Microsoft will mandate developers continue to support ESRAM on the older Xbox One systems, but they won’t be including it with Scorpio. “ESRAM remains essential to achieving high performance on both Xbox One and Xbox One S,” the whitepaper states. “However, Project Scorpio and PC are not provided with ESRAM. Because developers are not allowed to ship a Project Scorpio-only SKU, optimizing for ESRAM remains critical to performance on Microsoft platforms.” In fact, Microsoft still recommends developers use some of the same tactics to save bandwidth and reduce memory pressure while rendering to Xbox Scorpio, even though that platform will have vastly more resources to work with.
Project Scorpio is confirmed to have a 6TFLOP GPU, with total compute power rated as 4.5x the capability of Xbox One, with 4x more L2 cache. There’s nothing terribly informative in these specifications, since they don’t say if Scorpio is based on AMD‘s Vega or its Polaris family. Given that the platform’s memory type and total RAM have yet to be announced, this could still go either way. There’s been speculation Scorpio could use AMD’s newer Ryzen architecture rather than the older Jaguar part, but Eurogamer thinks that’s less likely based on some comments in the PDF. The paper makes reference to how developers may spend their new graphics firepower, noting increased resolution isn’t mandatory and other uses are permitted. It also states, “Another option developers might consider is frame-rate upscaling — running graphics at 60Hz but the CPU at 30Hz and interpolating animation.”
Interpolating animation sounds similar to what some HDTVs do to artificially boost frame rates. The image below shows how three frames of animation can be combined and processed on-the-fly to create five frames of displayable content. I’m not sure if any games have explicitly used this technique and presumably it would be something you can disable if you didn’t like the way the image looked.
Eurogamer thinks Microsoft likely stuck with Jaguar CPUs, since a more powerful CPU core wouldn’t require frame rate upscaling in the first place. This is certainly possible, but as with the PS4 Pro, there may be other things Microsoft did to increase Jaguar performance. It’s still possible the new SoC is unified (rather than being two quad-core blocks) and Jaguar’s L2 cache could’ve theoretically been brought up to full processor speed. A straight processor clock improvement would also offer higher performance — AMD’s A8-7410 was a Jaguar derivative with a 2.2GHz core clock and a 2.5GHz Turbo frequency with a 15W TDP. It wouldn’t be surprising if Microsoft debuted an eight-core Scorpio at, say, 2.5GHz. That would give them a 44% improvement in clock speed alone, and offer commensurate performance benefits in CPU-limited workloads.
Will the Xbox Scorpio offer 4K?
This is the major question a lot of gamers are going to ask, but we suspect the answer is much the same as it was for Sony’s PlayStation 4 Pro. The Xbox One’s increased memory bandwidth and GPU horsepower certainly put 4K in reach. But given Xbox One titles typically target 900p, not 1080p, rendering “native” 4K is 5.76x more pixels than 900p — and developers may prefer to do something else with their horsepower besides throw it at resolutions.
Our guess is Microsoft will take an approach similar to Sony and offer developers a range of options they can pick and choose from. As with the PS4 Pro, simple games and previous generation ports should have little trouble scaling up to 4K, but higher-end demanding games probably won’t make the jump to native 4K resolutions. Instead, developers can use a variety of upscaling techniques to get near-4K resolution for much better overall performance. Rasterization efficiency also improves as resolution increases, meaning the impact of scaling up to 4K increases pixel processing by 3.5x compared with 1080p, rather than a linear 4x.
Game developers are also encouraged to use techniques like sparse rendering and half-resolution rendering to reduce the performance impact of various effects.
“On Project Scorpio, a half-resolution effect rendered at 1080p and bilaterally up-sampled to 4K could look as good or better than the same effect rendered at full resolution on Xbox One,” the whitepaper states. “For example, on Xbox One, the effect is produced at full resolution, say 900p, but on Project Scorpio, the effect is produced at 1080p, which is half resolution.”
Here’s our take, based on what we know to date: Both the Xbox Scorpio and the PS4 Pro are technically capable of 4K resolution, subject to developer preferences, performance targets, and visual priorities. A developer might, for example, choose to offer 60fps at 1080p, or to spend more GPU horsepower on particle effects, lighting, and ambient occlusion.
Between the two consoles, Xbox Scorpio has stronger specifications and is therefore more likely to hit “native” 4K resolution or to offer a higher frame rate over the PS4 Pro at the same resolution. We do not know how these paper gains will translate to real titles and we do not know if Xbox developers will have the option to patch support for Scorpio’s features into earlier Xbox One titles or not. So far, Sony’s PS4 Pro rollout has been fairly good, but there have been some performance hiccups and issues related to the PS4 Pro that still need to be addressed.
As for which console is likely to be a better buy, that’s going to depend on how much you’ve bought into the existing generation, whether you have a 4K or HDR television, and how Microsoft prices the Xbox Scorpio. This is going to be a significant upgrade over Xbox One, but we still don’t know if MS will target $400, $500, or something higher for its new platform — and that’ll impact how it compares with the PS4 Pro.