Surface Pro X Sq2 SideSource: Daniel Rubino / Windows Central

What you need to know

  • Microsoft announced ARM64EC, which allows developers to mix and match different types of code for Windows 11 on ARM apps.
  • ARM64EC allows developers to switch part of an app's codebase to run on ARM natively while other parts of the app run in emulation.
  • The technology also lets developers make apps for Windows 11 on ARM even if they have dependencies that run on x64.

Microsoft announced a new technology called ARM64EC (Emulation Compatible) this week. It allows developers to switch over parts of their apps to run natively on Windows 11 on ARM devices. This means that developers can incrementally transition their apps to run on ARM. It's a major boost for the development of Windows 11 on ARM apps and should open doors for apps that couldn't migrate due to certain dependencies.

Some apps have plugins and dependencies that don't support ARM. Until ARM64EC, any app with one of these dependencies or plugins couldn't be made to run natively on Windows 11 on ARM (or Windows 10 on ARM). Microsoft explains the current limitations in a developer blog post.

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"Traditionally, rebuilding an app for ARM has meant recompiling the entire app. The result is a great native experience for the customer that unlocks the full power of the ARM device," explains Microsoft. "However, from a developer perspective, porting an app can be all-or-nothing, since all the binaries within a process need to be rebuilt before a customer can see the benefit."

In contrast to the current options, ARM64EC lets developers pick and choose parts of an app to switch over to native performance. Any parts recompiled with ARM64EC will perform with native speeds while the rest of the app will run in emulation.

With ARM64EC, developers can pick the most important part of their apps to switch over to native ARM performance. They can then migrate the rest over as they have more time or as dependencies gain support for ARM.

Microsoft rebuilt the binaries of Windows 11 on ARM with ARM64EC, which allows system code loaded by x64 apps to run with native speed. Microsoft's Office team also used ARM64EC to make the upcoming 64-bit Office for ARM that can use x64 plugins.

Developers can download the latest Windows Insider SDK and Visual Studio Preview to start working with ARM64EC. A Microsoft doc also has steps to help add ARM64EC configuration.

Microsoft promises more information about ARM64EC in the future, presumably including when it will be generally avaialble.

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