Comment by open-paren
9 days ago
> FEX allows you to run x86 applications on ARM64 Linux devices, similar to qemu-user and box64. It offers broad compatibility with both 32-bit and 64-bit binaries, and it can be used alongside Wine/Proton to play Windows games.
> It supports forwarding API calls to host system libraries like OpenGL or Vulkan to reduce emulation overhead. An experimental code cache helps minimize in-game stuttering as much as possible. Furthermore, a per-app configuration system allows tweaking performance per game, e.g. by skipping costly memory model emulation. We also provide a user-friendly FEXConfig GUI to explore and change these settings.
> On the technical side, FEX features an advanced binary recompiler that supports all modern extensions of the x86(-64) instruction set, including AVX/AVX2. The heart of this recompiler is a custom IR that allows us to generate more optimized code than a traditional splatter JIT. A comprehensive system call translation layer takes care of differences between the emulated and host operating systems and implements even niche features like seccomp. A modular core enables FEX to be used as a WoW64/ARM64EC backend in Wine.
Used by the new Steam Frame (https://store.steampowered.com/sale/steamframe) which is an ARM64 Snapdragon 8 Gen 3 that will run PC and PCVR gaming titles.
CodeWeavers' Crossover just released a Preview version for Arm that incorporates Fex and allows games like Cyberpunk 2077 to run: https://www.codeweavers.com/blog/mjohnson/2025/11/6/twist-ou...
I've tested it on an Ampere workstation, and was trying it on a Pi, but it seems with Trixie, there may be some bugs with both that and box64 right now, I was having trouble with both of them.
Hey, it's that YouTube guy with cursed Raspberry Pi setups!
Not just used by, Valve is sponsoring FEX.
https://news.ycombinator.com/item?id=45903610#:~:text=Valve%...
I wouldn't call this random comment reliable testimony that they are sponsoring FEX.
https://gamersnexus.net/pc-builds-news/valve-steam-machine-d... "Valve has devoted significant resources to the development of FEX emulation."
As the random commenter I agree. By "support" I meant that they have a line of product and a strategy that relies on FEX to work and work as seamlessly as possible.
If they contribute to FEX at even a fraction of what they did to wine and Proton it is indeed huge.
Man, Fex is Valve, Valve is Fex! The steam logo is right there in the logo!
https://files.mastodon.social/accounts/headers/110/652/595/6...
Center of left side, it is a Valve product. All main devs are employed by Valve.
Does that mean I can run windows games on my rpi? (In theory at least)
Yes (just possibly at ~2 fps)
Into the Breach is back on the menu.
There's probably a mountain of x86 games that would not need to hit above 15-30fps to be fun.
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It would be cool if we can use LLVM to lift the x86 code into LLVM bitcode and go to different platforms easily with ostate of the art optimizations, won't it?
Been there, done that during my PhD (code: [1]). Works reasonably well, except for compile times (for which I implemented a caching strategy). However, due to calling conventions, using LLVM isn't going to give the best possible performance. Some features like signal handling are extremely hard to implement with LLVM (I didn't, therefore). Although the overall performance results have been good, it's not an approach that I could strongly recommend.
[1]: https://github.com/aengelke/instrew
Sadly compile times of LLVM-based recompilers make it impractical for competitive x86 emulation. We're not just talking a few single-frame stutters here and there, but considerable startup delays and pauses in-game.
LLVM's optimization passes also are less useful than you might think, since the vast majority of them is motivated by source->binary translation (like clang). They don't have much effect when recompiling an already optimized binary to another architecture.