Understanding CPU Translation Layers: ARM to x86/x64 for Windows, macOS, and Linux

Understanding CPU Translation Layers: ARM to x86/x64 for Windows, macOS, and Linux

As technology continues to evolve, the need for seamless interoperability between different hardware architectures becomes increasingly crucial. One significant aspect of this interoperability is the ability to run software compiled for one CPU architecture on another. This blog post explores how CPU translation layers enable the execution of ARM-compiled applications on x86/x64 platforms across Windows, macOS, and Linux.

Windows OS: Bridging ARM and x86/x64

Microsoft’s approach to running ARM applications on x86/x64 hardware is embodied in Windows 10 on ARM. This system allows ARM-based devices to run Windows efficiently, incorporating several key technologies:

  • WOW (Windows on Windows): This subsystem provides compatibility for 32-bit x86 applications on ARM devices through a mix of emulation and native execution.
  • x86/x64 Emulation: Windows 10 and 11 on ARM can emulate both x86 and x64 applications. The emulation layer dynamically translates x86/x64 instructions to ARM instructions at runtime, using Just-In-Time (JIT) compilation techniques to convert code as it is needed.
  • Native ARM64 Support: To avoid the performance overhead associated with emulation, Microsoft encourages developers to compile their applications directly for ARM64.

macOS: The Power of Rosetta 2

Apple’s transition from Intel (x86/x64) to Apple Silicon (ARM) has been facilitated by Rosetta 2, a sophisticated translation layer designed to make this process as smooth as possible:

  • Dynamic Binary Translation: Rosetta 2 converts x86_64 instructions to ARM instructions on-the-fly, enabling users to run x86_64 applications transparently on ARM-based Macs.
  • Ahead-of-Time (AOT) Compilation: For some applications, Rosetta 2 can pre-translate x86_64 binaries to ARM before execution, boosting performance.
  • Universal Binaries: Apple encourages developers to use Universal Binaries, which include both x86_64 and ARM64 executables, allowing the operating system to select the appropriate version based on the hardware.

Linux: Flexibility with QEMU

Linux’s open-source nature provides a versatile approach to CPU translation through QEMU, a widely-used emulator that supports various architectures, including ARM to x86/x64:

  • User-mode Emulation: QEMU can run individual Linux executables compiled for ARM on an x86/x64 host by translating system calls and CPU instructions.
  • Full-system Emulation: It can also emulate a complete ARM system, enabling an x86/x64 machine to run an ARM operating system and its applications.
  • Performance Enhancements: QEMU’s performance can be significantly improved with KVM (Kernel-based Virtual Machine), which allows near-native execution speed for guest instructions.

How Translation Layers Work

The translation process involves several steps to ensure smooth execution of applications across different architectures:

  1. Instruction Fetch: The emulator fetches instructions from the source (ARM) binary.
  2. Instruction Decode: The fetched instructions are decoded into a format understandable by the translation layer.
  3. Instruction Translation:
    • JIT Compilation: Converts source instructions into target (x86/x64) instructions in real-time.
    • Caching: Frequently used translations are cached to avoid repeated translation.
  4. Execution: The translated instructions are executed on the target CPU.
  5. System Calls and Libraries:
    • System Call Translation: System calls from the source architecture are translated to their equivalents on the host architecture.
    • Library Mapping: Shared libraries from the source architecture are mapped to their counterparts on the host system.

Performance Considerations

  • Overhead: Emulation introduces overhead, which can impact performance, particularly for compute-intensive applications.
  • Optimization Strategies: Techniques like ahead-of-time compilation, caching, and promoting native support help mitigate performance penalties.
  • Hardware Support: Some ARM processors include hardware extensions to accelerate binary translation.

Developer Considerations

For developers, ensuring compatibility and performance across different architectures involves several best practices:

  • Cross-Compilation: Developers should compile their applications for multiple architectures to provide native performance on each platform.
  • Extensive Testing: Applications must be tested thoroughly in both native and emulated environments to ensure compatibility and performance.


CPU translation layers are pivotal for maintaining software compatibility across different hardware architectures. By leveraging sophisticated techniques such as dynamic binary translation, JIT compilation, and system call translation, these layers bridge the gap between ARM and x86/x64 architectures on Windows, macOS, and Linux. As technology continues to advance, these translation layers will play an increasingly important role in enabling seamless interoperability across diverse computing environments.