Microsoft Details Windows 10 on ARM

Posted on May 11, 2017 by Paul Thurrott in Windows 10 with 65 Comments

Microsoft today released a prerecorded video timed for Build 2017 that details Windows 10 on ARM and how its x86 emulation software works.

You can watch the video for yourself, of course, and it’s only 13 minutes long. But here are the highlights.

Why Windows 10 on ARM? As Terry Myerson explained last December when this initiative was first announced, Windows 10 on ARM seeks to address key customer needs: Always-on connectivity through the addition of integrated LTE capabilities and great battery life.

It’s not Windows RT. Windows 10 on ARM will offer the full desktop experience, including iconic Windows 10 features like Cortana, Edge, and Windows Hello. It will include the same apps and work with all Store apps, plus x86 Win32 apps in emulation.

It is Windows 10 Pro. The demo machine (see below) is running a 64-bit version of Windows 10 Pro on an 8-core Qualcomm Snapdragon 835 processor with 4 GB of RAM. It’s “real” Windows 10 Pro, too, meaning that windows 10 Pro-specific features like domain join work as expected.

It’s not even close to ready yet. As the Microsofties in the video demonstrate, they’re using an early engineering sample provided by Qualcomm to run Windows 10 on ARM. It’s not a laptop or a hybrid device, but just a black box. The final devices will be “2-in-1s and laptops” from a variety of PC makers, they say.

It will have “great” device support. In addition to running Windows apps, Windows 10 on ARM supports a wide range of modern (often USB-based) devices using in-box (and ARM-based) class drivers. (This is going to be an issue with Windows 10 S, by the way, since you can’t run x86 Setup utilities on that system.)

The x86 emulation layer works. Native apps like Edge, of course, work normally, but this system’s ability to run x86 apps is, of course, of more interest. Based on the handful of x86 apps they run in the video, performance looks solid.

How does it work? According to Microsoft, running x86 apps (normal desktop apps) is transparent to the user (and to the developer of those apps); they just work normally as on any other PC. Emulation works as it always has in Windows: There is a WOW layer (Windows On Windows) that abstracts the underlying kernel, drivers, and other system components and makes the PC/OS look and work like the real thing. 64-bit Intel versions of Windows 10 do the same thing when running 32-bit code too. But the CPU isn’t emulated in software; that happens in hardware. On ARM, CPU emulation happens in software.

UWP apps run better. x86 run, but you will of course have the best experience with native UWP apps. These apps won’t task the processor, RAM, or battery as hard as emulated x86 code. They’re native to ARM on this platform.


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