> 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.
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.
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.
> The heart of this recompiler is a custom IR that allows us to generate more optimized code than a traditional splatter JIT.
I didn't know what 'IR' stands for in this context, but according to ChatGPT it is 'Intermediate Representation', explaining it as follows:
> In compiler, emulator or JIT-compiler contexts, an IR is a representation of code that sits between the source (or original machine code) and the final target machine code.
For those who are not into compilers: 'JIT' stands for 'just in time', so a JIT-compiler is a compiler that compiles code during execution of the program (game), just in time for when it is needed, instead of compiling it once before executing.
I'n incredibly impressed by valve's commitment to playing the long game. It makes sense to have the frame by arm since the system is lighter and its clear this is just the trojan horse to get arm linux into every gamer's house. I wouldn't be surprised if we end up with an arm steamdeck 1-2 version from now when the tech is ready.
Too bad Arm doesn't allow architectural licenses, because this is exactly the kind of thing Valve and the FEX developers would want to extend the ISA to support. I bet we see a RISC-V backend to FEX in the next 6 months, it probably already exists in a private repo.
FEX is the shootstring, extra special discount budget (not maligning) version of Rosetta. Apple should sell Rosetta to Valve.
My understanding is that Rosetta sidesteps a bunch of tricky memory model issues by using non-standard hardware extensions only present in Apple Silicon, so even if Apple did share Rosetta, which they certainly won't, it wouldn't work properly on Valves hardware anyway.
yeah that is correct. The m series chips can turn on total store ordering memory model solely for Rosetta. There's also some hardware extensions to arm to support x86 condition codes in the hardware because it's way more instruction efficient that way.
The latter is now an optional feature in the mainstream Arm ISA now (FEAT_FlagM and FEAT_FlagM2). Similarly the “alternate floating point mode” that Apple uses to match nuances of x86 FP semantics is a standard architectural feature as well. The TSO option though is Apples own thing.
> Apple M1 has an undocumented extension that, when enabled, ensures instructions like ADDS, SUBS and CMP compute PF and AF and store them as bits 26 and 27 of NZCV respectively, providing accurate emulation with no performance penalty.
ARM were perfectly fine getting the bad press for suing Qualcomm for releasing the Snapdragon that was finally performing enough despite these companies paying them a lot of money.
They seemed quite happy to destroy their eco system if they won.
Rosetta performance is best in class to my knowledge, although they had the benefit of being able to add custom instructions and modes to the cpu to make some parts easier. Meaning Rosetta would not have helped valve unless they built the frame on apple silicon.
As for not improving, it is likely that Apple no longer feels the need to invest in Rosetta improvements now that Apple silicon is so dominant and software support is already very strong, but nothing is stopping them from investing in it if they need it for example for gaming
Why would a company on its way to the moon, entrust such an important project as translation layer between two major architectures to a single rinky-dinky corp that got rich selling common electronics marketed as luxury fluff, that's on the decline and has head so far stuck up its butt that it thinks it can do whatever it wants, instead of just write it themselves with support of the global developer community?
Apple could never do games because there are no luxury games. That's completely out of their zone of comprehensibility.
The AAA games industry with their multi-million budgets and "being too big to fail" mentality is on decline. It seems that anything that is not a new Call of Duty is considered not worth by the industry.
But smaller games and indie studios are thriving. We got lots of very interesting indie games this year.
Last I heard, they don't even have bosses there, a flat hierarchy. They vote on things and pick each other to work on teams and appraise performance. Perhaps that radical culture has merit to it?
I would keep in mind that the results reported there are likely quite a bit lower (in terms of CPU-side performance) than what you could achieve in practice, because it's running all of x86 Steam+Proton in the emulator. In a pre-configured environment (like SteamOS for ARM), the Steam client and Proton itself would be native ARM code, and emulation would stop at the win32 API boundary (or at certain critical libraries' APIs if you're using Linux apps).
How does fex deal with the fact that the memory model on arm is weak and x86 is total store ordering. It seems like would need to hammer performance by putting memory barriers everywhere to handle all cases. Perhaps fex only works when there are well defined mutexes it can gain visibility into? anyone know?
Looks like they do expensive conservative TSO emulation by default, but they're able to piggyback on compiler work that Microsoft did to make newer Windows x86 binaries easier to emulate. Since MSVC 2019 they annotate the executable with metadata that informs an emulator of when TSO is or isn't needed for correctness.
FEX also has settings which weaken or disable TSO altogether, favoring performance over correctness. You wouldn't want to rely on those for anything important but a game possibly crashing isn't the end of the world.
It would be nice to see more Arm chips adopt Apple's approach (which fixes this problem) for Rosetta 2. Basically, Apple's chips can be switched into a TSO mode and a few other minor tweaks that make x86 code run much, much faster.
I think that's right, there is no better way than just adding barriers. On Apple hardware it can probably make use of the special memory ordering mode, but on normal ARM64 there's probably nothing it can do.
One problem I see is that (e.g.) Qualcomm Adreno GPUs don't even run most Windows games well when executed natively under Windows, due to games only being optimized for GeForce and Radeon. I assume this problem only gets worse when trying to run DirectX games through some sort of translation layer with FEX/DXVK.
Denuvo anti-tamper DRM doesn't use kernel level tricks, it's all userspace and works just fine on Linux/Proton.
It's the kernel level anti-cheats that don't work on Linux. And some user level anti cheats (like AntiCheat Expert) that only work on the Steam Deck as they check the CPU/GPU of the system and refuse to work if it's not the one in the Steam Deck (which also means those don't work on platforms like the ROG Ally).
That issue only happens if there are other issue with the game unrelated to denuvo on wine which requires trying different prefixes resulting in the DRM locking you out. Its the fault of the horrible DRM.
Anyone can recommend something viable for simple tasks? I don't need 32GB of VRAM, just a reliable machine for everyday tasks that's decent, lightweight, has a good battery.
(I know I'm describing an M2 Air, but I'd like to explore alternatives.)
Not for Linux they're not. IIRC Audio and camera don't work, and firmware is non-redistributable and so you need to mooch it off a Windows partition. On top of that the performance on Linux hasn't been great either.
That's true Qualcomm in general, but is fortunately outdated for the Snapdragon Elite X (and only the X). Qualcomm has been upstreaming patches to Linus' tree[1] - but only for the Elite X - the Elite P processors get the classic Qualcomm treatment.
You're mangling Qualcomm's branding to the point that it's impossible to be sure what you're trying to say. Qualcomm's current laptop SoCs are called "Snapdragon X Elite" or "Snapdragon X Plus" or "Snapdragon X", all derived from various bins of two SoC designs, and all pretty much in the same boat for driver support purposes. "Snapdragon X2 Elite" and lesser siblings are due in the first half of next year, so a respectable degree of Linux support would mean having driver support for those chips in an upstream kernel release now so that there might be a mainstream distro supporting the hardware at some point in the quarter after the hardware ships.
> 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.
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.
https://news.ycombinator.com/item?id=45903610#:~:text=Valve%...
If they contribute to FEX at even a fraction of what they did to wine and Proton it is indeed huge.
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.
I didn't know what 'IR' stands for in this context, but according to ChatGPT it is 'Intermediate Representation', explaining it as follows:
> In compiler, emulator or JIT-compiler contexts, an IR is a representation of code that sits between the source (or original machine code) and the final target machine code.
For those who are not into compilers: 'JIT' stands for 'just in time', so a JIT-compiler is a compiler that compiles code during execution of the program (game), just in time for when it is needed, instead of compiling it once before executing.
There's probably a mountain of x86 games that would not need to hit above 15-30fps to be fun.
FEX is the shootstring, extra special discount budget (not maligning) version of Rosetta. Apple should sell Rosetta to Valve.
The JavaScript instruction is cooler though.
https://developer.arm.com/documentation/dui0801/g/A64-Floati...
> Apple M1 has an undocumented extension that, when enabled, ensures instructions like ADDS, SUBS and CMP compute PF and AF and store them as bits 26 and 27 of NZCV respectively, providing accurate emulation with no performance penalty.
You do want FEAT_AFP though, so you do want ARMv8.6+.
QEMU exists. I doubt they want the bad press of suing an Open Source project everyone is using.
They seemed quite happy to destroy their eco system if they won.
https://www.rcrwireless.com/20251001/business/qualcomm-arm-2
Isn't Rosetta kinda bad though? And won't get much better because it's not open source?
As for not improving, it is likely that Apple no longer feels the need to invest in Rosetta improvements now that Apple silicon is so dominant and software support is already very strong, but nothing is stopping them from investing in it if they need it for example for gaming
Why would a company on its way to the moon, entrust such an important project as translation layer between two major architectures to a single rinky-dinky corp that got rich selling common electronics marketed as luxury fluff, that's on the decline and has head so far stuck up its butt that it thinks it can do whatever it wants, instead of just write it themselves with support of the global developer community?
Apple could never do games because there are no luxury games. That's completely out of their zone of comprehensibility.
The games industry as a whole is in potentially terminal decline, have you seen all of the redundancies lately?
But smaller games and indie studios are thriving. We got lots of very interesting indie games this year.
Gabe Ownership/co-founder:
- Valve - Yacht Companies - Starfish Neuroscience (Neuralink) - Submarine Companies
https://interfacinglinux.com/2025/06/30/fex-emu-gaming-on-th...
https://fex-emu.com/FEX-2510/
FEX also has settings which weaken or disable TSO altogether, favoring performance over correctness. You wouldn't want to rely on those for anything important but a game possibly crashing isn't the end of the world.
A little old but still interesting.
https://www.gamingonlinux.com/2025/05/denuvo-will-lock-you-o...
(I know I'm describing an M2 Air, but I'd like to explore alternatives.)
1. https://www.qualcomm.com/developer/blog/2024/05/upstreaming-...