Valve Integrates FEX and Box64 Compatibility Layers into SteamOS for Steam Frame

New Compatibility Layers for SteamOS

Valve is introducing two new compatibility layers, FEX and Box64, into SteamOS for its Steam Frame headset. These additions complement the existing Proton compatibility layer, which allows Windows games to run on Linux-based SteamOS. The integration of FEX and Box64 aims to broaden the range of games playable on SteamOS-powered devices.

FEX: x86 Emulation on Arm

FEX is Valve's port of fex-emu, an open-source project designed to emulate x86 processor instructions on Arm chipsets. This emulator includes an advanced binary recompiler supporting modern x86(-64) instruction set extensions. It also utilizes graphics libraries like OpenGL and Vulkan to reduce overhead and employs code caching to minimize stuttering during gameplay.

Valve's Investment in FEX

Valve has been funding FEX lead developer Ryan Houdek since the project was a prototype, anticipating nearly a decade of development would be needed for it to become robust enough for widespread use. Houdek acknowledged Valve's support in allowing him to design and framework the project for long-term viability, both for Valve's use cases and as an open project adaptable by others.

Future of SteamOS on Arm Devices

With FEX now ready for integration into the Steam Frame headset, Valve is exploring versions of SteamOS for other Arm devices. Valve engineer Pierre-Loup Griffais indicated that the Steam Frame is paving the way for a more general SteamOS for Arm, suggesting that many devices could offer a good experience running SteamOS.