Prism Emulation For Windows on ARM Explained

In Short
  • Microsoft announced a new emulation layer called Prism on Windows 11 which can run x86 apps on ARM hardware with better performance and efficiency.
  • The new Prism translation layer also works for many Windows games and translates x86 binaries on the fly.
  • In an early report, an emulated app running on Snapdragon X Elite surpasses even native apps running on Intel processors.

At the Surface Event 2024, Microsoft launched Copilot+ PCs including Surface Laptop 7th Edition and Surface Pro 11th Edition, powered by ARM-based Snapdragon X series processors. During the launch event, Microsoft announced a new emulation layer called Prism to run x86-64 apps at near-native speed on ARM hardware.

prism emulation layer performance on windows
Image Courtesy: Microsoft

The Prism layer will debut with Windows 11 24H2 for the Windows on ARM (WoA) platform. Microsoft claims that the new Prism layer is as efficient as Apple’s Rosetta 2 and brings 2x faster performance in single-core tasks and 3x improvement in multi-core workloads, running under the emulation mode.

So in this article, we take a look at what Microsoft has done differently this time with its compatibility layer and should you be worried about running x64 apps on Copilot+ PCs.

Explained: Prism Emulation Layer on Windows on ARM

At the MS Build 2024 event, Microsoft touched on the new Prism emulation layer and explained some of the workings behind it. Microsoft says they have partnered with ARM to rebuild its Windows compiler in order to take advantage of Armv8 instruction set improvements.

It’s not just software, but ARM-based Snapdragon X series processors also offer hardware improvements for running x64 apps efficiently under the new emulation mode. Jon Masters, who is a computer architect for ARM servers at Google, also revealed that Armv8+ hardware offers many useful features for binary translation on the fly.

Apart from that, Microsoft has also rebuilt many Windows components and Runtimes to improve the CPU performance while running apps under the Prism emulation layer. In addition, system binaries are compiled using ‘profile guided optimizations’, a technique to improve the performance of an emulated app by optimizing it based on data collected from its actual execution.

As a result, you get an overall 2x performance jump with Prism emulation when compared to earlier efforts with the Microsoft SQ3 processor. Microsoft also expects that users will be spending up to 90% of application minutes on native ARM software. The company has been working with developers to bring native apps to the Windows on ARM (WoA) platform.

app list for windows on ARM
Image Courtesy: Microsoft

From first-party Microsoft apps to social media apps, entertainment apps, creativity apps, security solutions, and development tools, almost all of them now offer ARM native apps for Windows 11. You can find a list of native Windows ARM software from here.

Prism Emulation Layer for Gaming on Windows

As for gaming, the Prism layer is said to be quite impressive. It can translate x64 binaries to ARM64 instructions on the fly. Not just that, it can also translate drivers for the Adreno GPU and Windows libraries under emulation. And both translated drivers and Windows libraries run at near-native speed which is pretty remarkable.

snapdragon x elite arm64ec layer for gaming
Image Courtesy: Sean Hollister / The Verge

Microsoft showed a demo where Baldur’s Gate 3 ran under the emulation mode, yet delivered around 25 to 35 FPS. In the next example, Borderlands 3, running under emulation, crossed 35 FPS with Auto Super Resolution enabled.

While these demos are cool, we need to wait and see how the Prism emulation layer performs for other titles. By the way, a Microsoft-backed website maintains a list of games playable on Snapdragon X series processors so go ahead and check it out.

Prism Emulation Performance on Surface Laptop 7th Edition

While Microsoft and other OEMs have not shipped their Copilot+ PCs yet, Microsoft has commissioned a report by Signal65 which evaluated the emulation performance of the Surface Laptop 7th Edition, powered by Snapdragon X Elite.

prism layer performance on windows 11
Image Courtesy: Signal65

The report says that while running Adobe Lightroom Classic under emulation on the new Surface Laptop, SD X Elite surpasses Intel’s 12th-gen Core i7 processor by 30%, which is running the application natively. That’s a startling revelation. And it matches the performance of Intel Core Ultra 7 155H while running under emulation.

In the Blender test, SD X Elite-powered Surface Laptop 7th Ed. offers 35% faster performance while running in the emulation mode. However, the Intel Core Ultra 7 155H and Apple’s MacBook Air M3 offer better performance here. But keep in mind, they are running the native version of the app.

The report concludes by saying:

Emulated performance on the new device is outperforming even the native performance of the 12th Gen Core i7 previous generation Surface Laptop 5 – an impressive feat that should settle the nerves of any consumer debating the purchase of a new PC using this processor.

It looks like the new Prism emulation layer is indeed pretty powerful and running x64 apps on the next-gen Copilot+ PCs would not be a big issue. In addition to that, developers are increasingly porting their apps for native ARM64 architecture which should make for even better performance and efficiency.

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