Before we delve into our tests, it’s essential to understand why emulation remains a critical component for Arm-based Windows machines. For decades, Windows has been synonymous with x86 and x86-64 architectures, primarily powered by AMD and Intel processors. The vast majority of software written for Windows has been compiled to run on these architectures by default.
After several attempts to integrate Arm support—remember the Microsoft Surface RT?—we are now witnessing the emergence of a dual-architecture Windows ecosystem: x86-64 and Arm-64, also known as Arch64. This shift is largely driven by Qualcomm’s Snapdragon PC processors, with the Snapdragon X being the latest addition. However, without emulation, running x86/x64 code directly on an Arm processor is impossible due to differing instruction sets.
Why Emulation on Arm-Based Windows Machines is Necessary
When you compile an application using tools like Visual Studio, it can produce binaries for both x86-64 and Arm architectures, allowing the application to run natively on both types of processors. This is great for new and updated applications, but many older applications may never be recompiled to run natively on Arm.
Despite the Windows on Arm initiative being over seven years old, countless apps remain x86-64-only. Therefore, an emulator is essential for running these apps on an Arm processor. Microsoft has supported Arm emulation since Windows 10, but this has always come with a performance penalty. With the release of Windows 11 24H2, this emulation has been revamped and is now called Prism.
Microsoft claims that even without an emulator, 90% of the total app minutes—where users spend most of their time—are in apps that have a native Arm version. This claim is based on a survey of user behavior in non-gaming apps in the US and UK. Big names like Netflix, Kindle, Handbrake, Unity, VLC, and Microsoft Office now offer Arm-native versions. Additionally, top apps like Google Chrome, WhatsApp, Zoom, Adobe Photoshop, Disney+, and Spotify will run natively on Copilot Plus PCs from day one. While this shows growing support for Arm-native versions, plenty of software (including games) still requires emulation.
Microsoft’s Claims and Performance Enhancements
During the Copilot Plus PC launch, Microsoft claimed that emulated apps on PCs running the Snapdragon X Elite are more than twice as fast as previous-generation Windows Arm devices running Windows 11 22H2. They state that users will experience twice the emulated performance when running Windows 11 24H2 on a Snapdragon X Elite platform.
This improvement is attributed not only to software advancements but also to the Snapdragon X Elite itself. Microsoft compared a Qualcomm 8cx Gen 3 machine to a Snapdragon X Elite, showing significant improvements in processor performance and some enhancements in the Prism emulator. The idea is that today’s user experience will be substantially better than before, which many argue is what matters most. However, to know exactly how much better Prism performs, one would need to test the same device before and after the update.
Our Results
To test the performance uplift on the software side, we evaluated the x86-64 versions of Firefox, Cinebench Release 23, and Handbrake on a Surface Pro X both before and after the Prism update. Here’s what we found:
- Firefox: The browser showed noticeable improvements in speed and responsiveness post-update.
- Cinebench Release 23: Rendering times were significantly reduced, indicating better utilization of the hardware.
- Handbrake: Video encoding tasks completed faster, showcasing enhanced performance in resource-intensive applications.
These results underscore the importance of emulation on Arm-based Windows machines and highlight the progress being made in this area.
