A new Windows Insider test build seeks to solve one of the more frustrating problems with Windows on Arm: when an application simply doesn’t work.
Build 27744 within the Microsoft Windows 11 Canary Channel contains a new version of Microsoft’s Prism emulator, with a key addition: Prism now supports legacy AVX as well as AVX2 instructions. “You may find some games or creative apps that were blocked due to CPU requirements before will be able to run using Prism on this build of Windows,” a post describing the new build explains.
This is a big deal. Microsoft Windows runs applications written for either x86 or Arm processors, though the version of Windows has to match up with the specific instruction set. Because the vast majority of Windows apps were written for x86, Microsoft co-developed an emulator, called Prism, that can be used to allow x86 apps to run on Arm. In most cases, Prism can step in and allow those x86 apps to run on processors like the Snapdragon X Elite. In certain cases — games, mainly — the app simply won’t run at all. That’s what this new update is designed to address.
Microsoft isn’t saying which apps will be affected, save for Adobe Premiere Pro on Arm. That app was specifically included in the version of Prism which is currently within Windows 11 24H2, or the Windows 11 2024 Update. Now, the new build will expand that support “to any x64 application under emulation,” Microsoft says.
So far, the key applications that have been largely excluded from the Windows on Arm ecosystem have been games, though Microsoft did not specifically call those out in its announcement.
“At a technical level, the virtual CPU used by x64 emulated applications through Prism will now have support for additional extensions to the x86 instruction set architecture,” Microsoft says. “These extensions include AVX and AVX2, as well as BMI, FMA, F16C, and others, that are not required to run Windows but have become sufficiently commonplace that some apps expect them to be present.”
The only catch is that this updated version of Prism is designed with 64-bit applications in mind. Older 32-bit apps, or apps with a 32-bit helper, won’t detect the new features within Prism, Microsoft says.
Qualcomm has been steadily making progress in working with developers to code new Arm-specific versions of apps like Google Drive and VPN applications like NordVPN and ExpressVPN, which Qualcomm announced at IFA. Still, allowing Prism to “fill in” the gaps with improved instruction support is a big step for Windows on Arm, and evidence that Prism will continue to evolve and improve.
