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FEX-emu – Run x86 applications on ARM64 Linux devices
- cultofmetatron 10mo agoI'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.
- sitkack 10mo agoToo 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.
- JoshTriplett 10mo ago> Too bad Arm doesn't allow architectural licenses QEMU exists. I doubt they want the bad press of suing an Open Source project everyone is using.
- happymellon 10mo agoARM 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. https://www.rcrwireless.com/20251001/business/qualcomm-arm-2 https://www.rcrwireless.com/20251001/business/qualcomm-arm-2
- anthk 10mo agoAnd GBA emulators. And before that, BBC Accorn ones with Risc OS.
- geerlingguy 10mo agoBox64 already runs on RISC-V. Just, the available processors are so slow it's hard to even play 5-10 year old games.
- snvzz 10mo agoThis means that, when the much faster chips implementing RVA23 arrive next year, they'll be immediately able to run Box64.
- jsheard 10mo agoMy 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.
- fooblaster 10mo agoyeah 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.
- sgerenser 10mo agoThe 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.
- astrange 10mo agoIf you mean FEAT_FlagM, that's standard in ARMv8.4. (There's also FlagM2 and AFP that are optional.) The JavaScript instruction is cooler though. https://developer.arm.com/documentation/dui0801/g/A64-Floating-point-Instructions/FJCVTZS https://developer.arm.com/documentation/dui0801/g/A64-Floati...
- gorkish 10mo agoRISC is dead; long live RISC
- astrange 10mo agoIt's not only present in Apple Silicon, it's just not required by the ARM standard. Fujitsu also has an ARM64 CPU with TSO.
- nullbyte808 10mo agobetter yet, Apple should make it open-source on github.
- scotty79 10mo ago> Apple should sell Rosetta to Valve. Isn't Rosetta kinda bad though? And won't get much better because it's not open source?
- MobiusHorizons 10mo agoRosetta 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
- scotty79 10mo agoRosetta is abandonware: https://developer.apple.com/documentation/apple-silicon/about-the-rosetta-translation-environment https://developer.apple.com/documentation/apple-silicon/abou... 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.
- dontlaugh 10mo agoI don’t know if the two companies have such different futures. The games industry as a whole is in potentially terminal decline, have you seen all of the redundancies lately?
- kokada 10mo agoThe 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.
- deleted 10mo ago[deleted]
- LeFantome 10mo agoYou are looking for Felix86 https://felix86.com/ https://felix86.com/
- clausecker 10mo agoARM already has most stuff required for this on board. Two proprietary extensions are used by Rosetta: one emulates the parity (rarely used) and half-carry (obsolete) flags, which can also be emulated conventionally. The other implementa TSO memory ordering, which can either be ignored or implemented with explicit barriers; some other chips apparently have a similar setting. The other stuff is all present in ARMv8.5 I think.
- theoldgreybeard 10mo agoIt’s amazing what you can do when you have a business that prints money hand over first and you have no obligations to shareholders.
- notepad0x90 10mo agoLast 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?
- wmf 10mo agoAnything works when you have infinite money and the company is privately owned by a chill dude.
- systematizeD 10mo agoHow much did Gabe own Valve, 50%? Gabe Ownership/co-founder: - Valve - Yacht Companies - Starfish Neuroscience (Neuralink) - Submarine Companies
- bbminner 10mo agoI've heard that to ship hl2 (or anything really) they had to stip some of that flatness somewhat.
- pjmlp 10mo agoI would appreciate more if they also would take devs into SteamOS water, instead of relying on Microsoft kindness.
- Havoc 10mo agoHelps that they are in dominant position and basically just need to not fuck up
- Venn1 10mo agoI tried out FEX on a modern ARM board with a discrete GPU. Really impressed with the performance. https://interfacinglinux.com/2025/06/30/fex-emu-gaming-on-the-on-the-orion-o6/ https://interfacinglinux.com/2025/06/30/fex-emu-gaming-on-th...
- roody15 10mo agoWow decent results.. impressed.
- Plagman 10mo agoI 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).
- Lightkey 10mo agoFancy seeing the Plagman here. Last time I saw you was on Freenode (R.I.P.). So you are still working for Valve? ;-)
- TinkersW 10mo agoFEX is a CPU JIT, so your GPU settings are irrelevant to it, it is translated but not by FEX, and there is no real perf hit for the GPU The old games don't really matter with regards to FEX perf, so the only relevant bit is the semi newer games at 30/40 fps, which seems very slow to me, given that you are only running at 1080p/Medium, so you likely have a CPU bottleneck there.
- fooblaster 10mo agoHow 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?
- nialv7 10mo agoI 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.
- ant6n 10mo agoThere’s one trick: run those threads on one cpu. But that may be slower than barriers on multiple CPU’s, unless the code uses a lot of library code that can be emulated directly, separately on other cpus.
- jsheard 10mo agoLooks 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. https://fex-emu.com/FEX-2510/ 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.
- nullbyte808 10mo agoNow we just need a decent ARM Linux laptop.
- overfeed 10mo agoSnapdragon Elite X laptops are plenty decent.
- ben-schaaf 10mo agoNot 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.
- LeFantome 10mo agoHighly depends on which laptop
- donkeylazy456 10mo agoQualcomm's linux support is not.
- overfeed 10mo agoThat'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. 1. https://www.qualcomm.com/developer/blog/2024/05/upstreaming-linux-kernel-support-for-the-snapdragon-x-elite https://www.qualcomm.com/developer/blog/2024/05/upstreaming-...
- wtallis 10mo agoYou'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.
- jasonjmcghee 10mo agoCurious how this will impact the major games that are incompatible due to denuvo type stuff
- paulryanrogers 10mo agoIIUC that DRM involves kernel level tricks and attestation, which means it'll basically never happen. Online gaming looks similarly doomed.
- dralley 10mo agoPlenty of online games work fine. Rocket League, Squad, Arc Raiders etc. are just the ones that I play.
- rounce 10mo agoIn the case of those which use EAC/EOS they need to be explicitly approved to run under Wine/Proton by the developer. There are some cases (eg. iRacing) where the developer refuses to enable support for whatever reason, and on those we’re still stuck.
- ThatPlayer 10mo agoIt's not just 'running under Wine', it's a different anti-cheat with different capabilities and the same name. It's like comparing Office 2024 Excel on Windows to Excel for iPad. They're both called Excel, and share basic features, but once you start using features like VBA, it will not run on iPad Excel. Also does it even work in Wine? Last I checked EAC only worked in Proton with the env variable to enable it being PROTON_EAC_RUNTIME
- deleted 10mo ago[deleted]
- sintax 10mo agoDenuvo 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).
- yakaccount4 10mo agoI believe a lot of the folks working on FEX are also core contributors to Dolphin, the Wii/GC emulator.
- zozbot234 10mo agoNope, Dolphin emulates PowerPC not ARM or ARM64. Totally different architecture.
- yakaccount4 10mo agoI was saying some of the top contributors of Dolphin are also top contributors of this project based on GitHub data.
- HelloUsername 10mo agoThat's really cool! I didn't know, thx for your comment :)
- cubefox 10mo agoOne 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.
- LeFantome 10mo agoThe GPU is not run through a translation layer. The GPU is not an x86-64 CPU. Only the CPU code has to be emulated. The GPU runs natively. That does not help with poorly supported GPUs of course.
- cubefox 10mo agoPretty sure the GPU doesn't understand DirectX, which is used for Windows games, so it must be run through a translation layer.
- scheeseman486 10mo agoWrapping graphics APIs adds effectively zero overhead if the featureset of the hardware and drivers are a close enough match.
- LeFantome 10mo agoSure, you are translating DirectX to Vulkan and that work is done on the CPU. So it may need emulation. But the Vulkan instructions passed to the GPU are effectively native. The amount of work the GPU has to do to execute against those calls is the same regardless of CPU architecture.
- Philpax 10mo agoSee the corresponding Igalia article for more details: https://www.igalia.com/2025/11/helpingvalve.html https://www.igalia.com/2025/11/helpingvalve.html
- skywal_l 10mo agoPresentation at FOSDEM2022: https://archive.fosdem.org/2022/schedule/event/fex/ https://archive.fosdem.org/2022/schedule/event/fex/ A little old but still interesting.
- pona-a 10mo agoHow is it different to box64? I couldn't really find much online comparing these two except a brench by box64 themselves.
- systematizeD 10mo agoNo different. Box64 only drm free game first, later they support drm games. Fex straight drm games.
- yonatan8070 10mo agoAre you referring to Linux's Direct Rendering Manager or to Digital Rights Management in this context?
- systematizeD 10mo agoDigital Rights Management
- hydroreadsstuff 10mo agoSome companies like to stress the efficiency or performance of Arm SoCs, but really this is a hedge against more expensive x86 hardware. AMD has increased prices of mobile SoCs radically recently. I'm looking forward to having more affordable SoC options for laptops, handhelds and desktops, perhaps from Mediatek or other lower-cost vendors. The history of the PC is one of commoditization. A fractured multi-polar landscape is detrimental to the ecosystem/productivity and should ultimately fail. x86 emulation is an important puzzle piece, and I'm happy Valve recognizes this and sponsors it.
- LeFantome 10mo agoThis is for the Steam Frame
- VikingCoder 10mo agoSo, can you run Steam and games on a Raspberry Pi 500?
- LeFantome 10mo agoYup
- VikingCoder 10mo agoLike, already, or in theory?
- alan-jordan13 10mo ago[dead]
- open-paren 10mo 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 https://store.steampowered.com/sale/steamframe) which is an ARM64 Snapdragon 8 Gen 3 that will run PC and PCVR gaming titles.
- sitkack 10mo agoNot just used by, Valve is sponsoring FEX. https://news.ycombinator.com/item?id=45903610#:~:text=Valve%20has,official%20now.&text=Valve%20deciding,to%20support https://news.ycombinator.com/item?id=45903610#:~:text=Valve%...
- cubefox 10mo agoI wouldn't call this random comment reliable testimony that they are sponsoring FEX.
- teroshan 10mo agoAs 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.