As noted, Project Scorpio was unveiled at E3 2016 as the "most powerful console ever made," but apparently, Scorpio wasn't intended for an E3 unveiling at all. The PlayStation 4 Pro leaks weeks prior led Microsoft to show their hand early, having previously only shown the early Scorpio dev kits to a few developers and publishers.
The change in plans might have been what led to the rumored Xbox streaming stick to being canceled, apparently at the last minute.
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The Coalition has previously confirmed that Gears of War 4 is ready to run at a 4K resolution on Project Scorpio. This is because Project Scorpio can run 4K Windows 10 Store Universal Windows Platform (UWP) games natively. If you've played Gears of War 4, Forza Horizon 3 or Rise of the Tomb Raider at a 4K resolution on a high-end PC, you already have an idea of how gorgeous games will look on Project Scorpio.
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Our source told us that any game programmed natively for UWP on Windows 10 will run on Project Scorpio with a trivial amount of changes. This has always been Microsoft's vision for UWP.
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Our source told us that Project Scorpio dev kits will be a "one-stop shop" for all Xbox platform development. Project Scorpio will be able to mimic an Xbox One at a hardware level so developers can test how their games scale between different power levels. This system is known internally as Project Helix.
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When a game is being run by a customer, it will detect the hardware making the runtime request and unpack the correct assets dynamically. Since UWP games on PC already support most Xbox features, including controllers, there will be a minimal amount of work involved when bringing PC UWP games to the Xbox consoles. Our source told us that games such as Gears of War 4, ReCore, Rise of the Tomb Raider and Forza Horizon 3 are already using this system on Xbox One and Windows 10 PCs today. There's also a fair chance the new Call of Duty on the Windows 10 Store is also using this system to prepare for Scorpio, but without seeing the app's manifest, there's no way to know for sure.
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Project Centennial in a gaming context, as demonstrated by Phil Spencer back at Build 2016, is a system that allows a developer to take a Win32 game (typical of Steam) and easily wrap it for deployment on the Windows 10 Store. Microsoft demonstrated how Win32 games like Age of Empires II HD and The Witcher 3 could be prepared for the Windows 10 Store as .appx files with relative ease.
However, according to our source, Project Centennial is not being used for Project Scorpio at all. Games packaged for UWP this way are still, at their core, Win32, which means that Project Scorpio and the Xbox One will not be able to run them. Some have speculated that Scorpio might have had a more PC-like architecture, allowing Centennial games to run on the system, paving the way for Windows sizable gaming backlog to hit the console. The fact Scorpio will require developers to build their games natively, either for UWP or via the XDK, ensures that Microsoft will keep their promise of Scorpio having no exclusives vs. the original Xbox One (with the exception of VR).
Finally, Project Scorpio will run on the Xbox One OS, with additional features that support VR and 4K gaming. Whether it will retain the same visual interface is unknown, but considering Project Scorpio is designed to sit alongside the Xbox One, rather than supersede it, it makes sense.