Unlock x86_64 Linux Apps on ARM64: A Step-by-Step Guide to FEX 2605 Emulator

Introduction

If you own an ARM64 Linux device—like a Raspberry Pi, a Snapdragon X Elite laptop, or any other AArch64 machine—you may have encountered the limitation of running x86_64 software natively. Thanks to the open-source FEX emulator, now in version 2605, you can bridge that gap. Sponsored by Valve, FEX 2605 brings significant performance improvements and initial fixes for the Snapdragon X2 Elite, making it a practical solution for running Linux x86_64 binaries on ARM64 hardware. Whether you’re a developer testing apps or a gamer exploring titles from the Steam Frame ecosystem, this guide will walk you through installing, configuring, and using FEX 2605 step by step.

What You Need

Before we begin, gather the following prerequisites:

• An ARM64 Linux system – Any modern distribution (e.g., Ubuntu, Debian, Fedora, Arch Linux ARM) running on AArch64 architecture.
• Basic command-line experience – Comfort with terminal commands and package managers.
• Git and build tools – For compiling FEX from source (latest features). Alternatively, you may use prebuilt packages if your distro provides them.
• Sufficient storage space – At least 2 GB free for the build process and runtime dependencies.
• Internet connection – To download source code, updates, and x86_64 libraries.
• Optional: Steam account – If you intend to run Steam games via FEX.

Step 1: Prepare Your System

Start by updating your package list and installing essential build dependencies. Open a terminal and run:

1. sudo apt update && sudo apt upgrade -y (for Debian/Ubuntu; adjust for your package manager).
2. Install git, cmake, ninja-build, python3, pip, and a C++ compiler: sudo apt install git cmake ninja-build python3 python3-pip g++
3. For Fedora: sudo dnf install git cmake ninja-build python3 gcc-c++
4. For Arch: sudo pacman -S git cmake ninja python python-pip base-devel

Step 2: Clone the FEX Repository

FEX 2605 is a monthly feature release. To get the latest source, clone the official GitHub repository:

1. git clone https://github.com/FEX-Emu/FEX.git
2. Navigate into the directory: cd FEX
3. Check out the latest tag (e.g., git checkout v2605) to ensure you have the stable release.

Step 3: Build FEX from Source

FEX uses a Python-based build system called BuildFEX.py. This step may take 15–30 minutes depending on your hardware.

1. Run python3 BuildFEX.py --Release --GCC to build an optimized release version (GCC recommended for best performance).
2. If you have multiple CPU cores, speed up with -j4 (adjust core count).
3. After compilation, install the binaries: sudo python3 BuildFEX.py --install

Step 4: Verify Installation

Check that FEX is correctly installed by running:

1. fex --version – should display version 2605 (or similar).
2. which fex – ensure it's in your PATH.
3. Test with a simple x86_64 binary (e.g., Hello World compiled for x86_64). If you don't have one, create it on an x86_64 machine or download from a trusted source.

Step 5: Configure FEX for Your System

FEX uses a configuration file to customize settings. Edge cases for Snapdragon X2 Elite users may require specific fixes included in version 2605.

1. Run fexcfg --init to generate a default config in ~/.fex/FEXConfig.json.
2. Edit the file to adjust options like CPUModel (set to SnapdragonX2Elite if applicable) or memory limits.
3. Enable Thunking for improved compatibility with certain libraries: fexcfg --set Thunking true

Step 6: Set Up Rootfs (Optional but Recommended)

FEX can use a root filesystem to provide x86_64 libraries and dynamic linker. You can download a prebuilt rootfs or create your own via fex-rootfs:

1. Use the built-in tool: fex-rootfs --download --distro ubuntu --version 24.04
2. Place it in an accessible location, e.g., /opt/fex/rootfs.
3. Tell FEX where it is: fexcfg --set RootFS /opt/fex/rootfs

Step 7: Run an x86_64 Program

Now you are ready to execute an x86_64 binary using FEX.

1. Navigate to the binary location.
2. Run: fex /path/to/your/x86_64-app
3. If using a rootfs, add --rootfs /opt/fex/rootfs for better library support.
4. For gaming via Steam, install Steam from the ARM64 repository, then use fex steam to launch it inside the emulator. Note: Performance improvements in version 2605 make this more viable, especially for lighter titles.

Step 8: Troubleshoot Common Issues

Encounter problems? Try these tips:

• Missing libraries: Install the needed x86_64 libraries in your rootfs using fex-rootfs --chroot and apt install.
• Graphics issues: Ensure your ARM64 GPU drivers are up-to-date. FEX supports OpenGL and Vulkan pass-through when available.
• Performance: For Snapdragon X2 Elite devices, the initial fixes in version 2605 address specific CPU quirks. If you still see slowdowns, tweak CPU model settings in the config.
• Check logs: Use fex --log-level=debug to see detailed output.

Tips & Conclusion

Congratulations! You’ve set up FEX 2605 on your ARM64 Linux machine. Here are some final pointers:

• Stay updated: FEX releases new features monthly. Watch the GitHub page or subscribe to the mailing list to receive performance boosts and compatibility fixes.
• Join the community: The FEX Discord and forums are active; you can report issues or share your gaming experiences.
• Use with caution: While FEX is stable for many apps, not all x86_64 binaries work perfectly. Complex software like high-end games may still hit limits—but version 2605 is a big step forward.
• Backup config: Before experimenting, copy your FEXConfig.json file so you can revert if something breaks.
• Explore Steam Frame: As Valve’s project matures, FEX will be integral to gaming on ARM laptops. Keep an eye on developments.

With FEX 2605, you’ve unlocked a world of x86_64 software on ARM64 hardware. Whether you’re running productivity tools, development environments, or Linux games, this emulator brings the power of an entire ecosystem to your fingertips. Happy emulating!