FEX-emu – Run x86 applications on ARM64 Linux devices

Original Article ↗ Hacker News Discussion ↗

Valve’s Role and Goals

  • FEX is closely tied to Valve’s new ARM-based Steam Frame; multiple comments say it is effectively a Valve-backed/initiated project, with developers employed or funded by Valve.
  • People see this as part of a long-term strategy to make ARM Linux a mainstream gaming platform (Steam Frame now, possibly future ARM Steam Decks).

Integration with Wine, Proton, and CrossOver

  • FEX is used in conjunction with Wine/Proton to run Windows titles; CodeWeavers has a CrossOver ARM preview integrating FEX, reportedly running heavy games like Cyberpunk 2077 on ARM servers and some SBCs.
  • Expectation that much better performance comes when Steam, Proton, and supporting tools are native ARM, with only Win32/x86 code going through FEX.

Performance and Technical Design

  • Users report surprisingly good performance on modern ARM boards with discrete GPUs, though some see 30–40 fps at 1080p as still CPU-limited.
  • FEX is a CPU JIT; GPU work remains native, with DirectX-to-Vulkan translation handled by tools like DXVK, not by FEX itself.

Memory Model / TSO Handling

  • Concern: x86’s strong ordering vs ARM’s weak model.
  • FEX reportedly emulates TSO conservatively with barriers by default, but can use MSVC 2019 annotations to avoid barriers where safe.
  • Per-app options allow weakening or disabling TSO for extra performance at the risk of instability in some games.

Hardware, Laptops, and OS Support

  • Many want “decent ARM Linux laptops.” Snapdragon X Elite laptops are viewed as promising but Linux support is mixed: some models work well with community/“concept” kernels, while others (notably some “Plus” variants) require more reverse engineering.
  • Asahi Linux on Apple Silicon is suggested but currently limited to older chip generations.

DRM, Anti‑Cheat, and Game Compatibility

  • Kernel-level anti-cheats remain a major blocker on Linux/ARM; user-mode DRM like Denuvo is said to work but can be fragile (e.g., lockouts when switching Proton versions).
  • Some anti-cheats only whitelist specific hardware (e.g., Steam Deck), limiting support on other ARM devices.

Comparisons and Ecosystem Impact

  • FEX is compared to box64 (similar goal, different maturity/DRM focus) and to historic/other binary translators like FX!32 and Rosetta 2.
  • Rosetta is considered technically “best in class,” helped by Apple-only ISA extensions (TSO mode, flag/FP tweaks), but closed and not portable.
  • Commenters see robust x86-on-ARM emulation as key to keeping the PC gaming ecosystem viable on cheaper, more power-efficient non-x86 hardware.