Not just Proton: Getting to know Valve's new SteamOS compatibility layers
New system-level tools bring Arm chipsets, Android APKs into the Steam ecosystem.
Since the launch of the Steam Deck, Valve enthusiasts have become well-acquainted with the Proton compatibility layer. This tool enables Windows-based games to perform adequately on Linux-based SteamOS. However, it's worth noting that Valve is now employing two additional compatibility layers to expand the range of games compatible with the SteamOS-powered Steam Deck.
The first of these is FEX, which is Valve's adaptation of fex-emu, an open-source project that emulates x86 processor instructions on an Arm chipset. Established in 2018, the project has evolved significantly, incorporating an advanced binary recompiler that accommodates all modern extensions of the x86(-64) instruction set. FEX can also interact with graphics libraries like OpenGL and Vulkan, thereby minimizing overhead and reducing stuttering.
As per Steam's developer documentation, FEX achieves this by utilizing code caching. Unlike Proton, which is built on the existing Wine conversion tool, FEX was originally developed by Ryan Houdek, who began as a prototype project funded by Valve. Valve engineer Pierre-Loup Griffais revealed to The Verge last year that the company had been supporting FEX's lead developer since the project's inception, anticipating that it would take nearly a decade before FEX-emu would be robust enough for widespread use.
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