Microsoft rebuilt Windows 11 around AI and Arm chips

There's also a new emulator, Prism, for running older Windows apps.

Devindra Hardawar / Engadget

Windows' Arm woes may finally be over. As part of the company's new Copilot+ AI PC initiative, which includes new Surfaces and partner systems running Qualcomm's Snapdragon X Elite chips, Microsoft says it has rebuilt core components of Windows 11 to better support Arm-based hardware and AI. That includes a new kernel, compiler, and most importantly, an emulator named "Prism" for running older x86 and x64 apps.

You'd be forgiven for being skeptical, though. Since the launch of the Windows RT-powered Surface in 2012, Microsoft has proven it can't be trusted to deliver a decent OS experience on Arm. That device couldn't run legacy x86 apps (who would want to do that in Windows, right?), and it was far slower than PCs with Intel and AMD CPUs. Windows on Arm slowly improved over the years, to the point where it had serviceable emulation on the Surface Pro 9 5G. But that slate still couldn't keep up with its Intel-equipped sibling, especially when it struggled to emulate popular apps like Chrome.

Microsoft says it reworked Windows 11 schedulers to take advantage of Arm capabilities and AI workloads. There's also a new driver compute model that recognizes neural engines more like how Windows sees CPUs and GPUs, as well as AI APIs built directly into the OS. Basically, Arm hardware should no longer feel like an afterthought and developers should be able to tap into AI capabilities more easily.

"So, effectively, we're building binaries and windows that are optimized with certain workloads," Pavan Davuluri, Microsoft's head of Windows and Devices, said in a briefing with reporters earlier this month. "The benefit for us for that is there are certain things that we know customers with Copilot+ PCs are going to do on an ongoing basis, and we can really focus on optimizing for those scenarios and making sure the machine responsiveness is a meaningful improvement."

Thanks to a powerful new Neural Processing Unit (NPU) in the Snapdragon X Elite chips, Copilot+ PCs can run more than 40 trillion operations per second, a measure of a chip’s AI performance, more than four times the performance offered by today’s AI PCs. Microsoft claims that this is twice the performance offered by Apple’s MacBook Air and MacBook Pro.

While Microsoft is pushing the availability of more native Arm apps for Windows 11, it's hard to deny the importance of supporting older software. That's where the Prism emulator comes in. Microsoft claims it improved the number of apps it supports, and that it's around 20 percent faster than its previous emulator. Any x86 and x64 apps that run under emulation with the Snapdragon X Elite Arm processors are more than twice as fast as previous generations of Windows that ran on Arm, Microsoft said in a blog post.

"When you combine the new Prism emulator with simply the raw performance and improvement in CPUs themselves, we're in a place where we have great native apps and we're also in a place where the breadth of the app catalog also has tremendous performance comparable to the rest of the Windows estate today," Davuluri said.

The NPU also lets Microsoft add AI-powered software features to Windows such as Recall, a new feature that uses AI to retrieve nearly anything you’ve seen on your PC, something that Microsoft compares to giving your computer a photographic memory. Another feature called Live Captions offers instant and real-time translations from 44 languages into English across any video or audio playing on your PC.

Catch up on all the news from Microsoft's Copilot AI and Surface event today!