Microsoft has introduced a new Application Binary Interface (ABI) called ARM64EC. This should allow applications to be created for Windows 11 on ARM processors that, according to the publisher, reach native speeds and should be compatible with x64 architectures. From now on it should be possible in this way to freely mix apps, processes and individual modules for ARM64EC and x64.
The “EC” in ARM64EC stands for “Emulation Compatible” and on the Microsoft side is a name for the new way of creating applications for Windows 11 on ARM. The applications created as emulation-compatible with ARM64 can contain x64 code, but do not have to: According to the announcement in the Windows Developer Blog, existing applications with the new technology should even achieve native speeds on ARM in the transition phase if there are dependencies and ARM plug-ins do not yet support.
Gradually adapt applications to ARM64
In the conventional process, adapting an application to the ARM architecture required the entire application to be recompiled. With Microsoft’s own application binary interface, porting should also work incrementally, i.e. in small steps. As a result, developers can select those parts of their code base that they would most like to give native ARM performance to, without first turning the entire code base of their application inside out. At the same time, x64 plug-ins should still be able to be loaded and integrated (“mix and match” principle).
According to the blog post the Microsoft team has already built the Windows 11 binaries on ARM internally with the new technology and any system code that an x64 application loads should run here at native speed. Also the upcoming 64-bit Office version for ARM should work on the same principle, can be found in the blog entry.
For now only accessible to Windows Insiders
If you are curious, you can get the ARM64EC with the Windows Insider SDK and the current one Visual Studio Preview Both downloads contain the ABI – Insider content is currently only available to members of the Windows Insider program. The corresponding chapters in the Microsoft documentation on ARM64EC configuration.