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Emulating x86: Microsoft builds granny flat into Windows 10

Park your legacy apps here, they'll feel right at home

Microsoft plans to emulate x86 instructions on ARM chips, throwing a compatibility lifeline to future Windows tablets and phones.

The Cobalt project should bear fruit within the year, when the "Redstone 3" release of Windows 10 is due to arrive, Mary Jo Foley reports. Ideally, Microsoft wants everyone to convert their old Windows apps to be UWP (Universal Windows Platform) apps, which are adaptable to different input methods and display sizes. So a phone or tablet to double up as an ad-hoc PC; a UWP "phone" app becomes a "desktop" app when docked to a larger display, and keyboard and mouse, via Continuum.

But a large proportion of business apps will never be converted, hence the need to run legacy apps too somehow. Intel dealt Microsoft's strategy a serious blow when it said it wouldn't announce any more new Atom smartphone chips until 5G came around. These chips support the x86/AMD64 instruction sets natively, and could (and probably would) have powered a Surface Phone.

A sharp-eyed developer found a reference to "CHPE" architectures as build targets in the header files of the SDK for Windows 10 build 14965.

Windows watchers were puzzled when support for next year's flagship Qualcomm MSM8998 processor (as yet unreleased) appeared, then disappeared, from Windows builds. Mary speculates that the Qualcomm part, most likely to be marketed as the Snapdragon 830, would contain hardware that better supports virtualisation. We can't corroborate that – but knowledgeable readers can get in touch.

Without native emulation available, HP opted for a streaming solution for its major Continuum-based effort around the Elite x3 (reviewed here), billed as a "three-in-one" for business.

Microsoft has to walk a fine line. Legacy x86/amd64 apps aren't "adaptable" and are unsuited to mobile use, having been written for full-blown PCs... but they do provide users with the jam they need today.

Microsoft had publicised a major Android emulation initiative for Windows 10, which allowed APK executables to run unmodified on Windows 10. This was called Project Astoria, and for a few surreal weeks, Android apps flooded onto Windows mobile via sideloading. But fearing this would remove any incentive for developers to create UWP apps, Microsoft canned the project.

So the instruction set that would never die gets to live a little longer – in a nice little granny flat. Aw. ®

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