Valve has enabled the FEX code cache in Proton Experimental for ARM, targeting better 1%-low frame times when Windows games run on ARM64 Linux hardware. Developer Pierre-Loup Griffais said the improvement should be particularly noticeable on subsequent runs, when translated code can be reused rather than generated again.
What the cache changes
FEX translates software built for x86 processors so that it can run on ARM64 Linux devices. It supports both 32-bit and 64-bit binaries and can work with Wine or Proton, providing the translation layer needed to run Windows games that were not built for ARM hardware.
The newly enabled cache stores ARM64 machine code produced during that translation. When the same code is needed later, FEX can retrieve the stored version instead of repeating the work. This is intended to reduce translation overhead, potentially improving game startup behavior and limiting some stutter during later sessions.
Frame consistency is the target
The stated benefit concerns 1%-low frame times, a measure focused on the slowest frames rather than average performance. Improving those lows can make gameplay feel more consistent even when headline frame rates remain unchanged. Valve has not supplied benchmark results or quantified the expected improvement, so the scale of the benefit is not yet established by the source.
Relevant to ARM gaming devices
The change applies specifically to the ARM version of Proton Experimental and is relevant to devices such as Steam Frame. It reflects work across FEX and Proton to reduce the performance costs of running x86 Windows games on a different processor architecture, rather than requiring every game to receive a native ARM64 build.
Caching has limits
FEX cannot create reusable cached translations for every part of a workload. The feature therefore addresses one source of overhead but does not guarantee uniformly faster startup or smoother play across all games. Results may depend on how much translated code can be retained and reused in subsequent runs.
AI-generated editorial illustration; not a documentary photograph.
Source: FEX code cache enabled for Proton Experimental (ARM) to improve frame timings
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