It turns out that not only are Valve using the open source FEX for the Steam Frame but they have been funding FEX since the beginning of it.
What exactly is FEX? 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.
Recently, the FEX lead Ryan Houdek wrote a 7 year anniversary blog post where in it they noted:
Hey everyone! In light of the recent product announcements using FEX, I wanted to take a moment to celebrate our anniversary! On this day seven years ago (28th Nov 2018), I landed the first commit in the prototype project that would eventually become FEX-Emu! I want to thank the people from Valve for being here from the start and allowing me to kickstart this project. They trusted me with the responsibility of designing and frameworking the project in a way that it can work long-term; not only for their use cases but also keeping it an open project that anyone can adapt for their own use cases.
This makes sense with the Steam Frame, since it will be using a Snapdragon processor - Valve needed a way to get traditional games and apps to work on it and not just those designed for it. Much like how Proton made sure the Steam Deck was a success and has pushed Linux overall to new heights, FEX should hopefully do the same for the Steam Frame and any other future hardware using Arm.
Unlike Proton though, which was based on the existing Wine project with some extras they also fund like DXVK and VKD3D-Proton, Valve was there for the formation of FEX.
In a fresh interview with The Verge, Valve developer Pierre-Loup Griffais confirmed:
Proton is also something where you could say we started it, but because it’s a derivative of Wine, it’s less clear-cut. Whereas Fex, we were talking with a few developers that we knew were the right fit for an undertaking like that, a long-term thing that needed a very specific set of experts. We worked hard on trying to convince these guys to start the project, and have been funding them ever since.
Don't go expecting a Steam Phone any time soon though it sounds like they're happy with living room, handheld, and desktop. But, since FEX is open source people are already using it to get Windows games running on phones.
It's all about giving options and removing barriers, so that you will hopefully eventually get the same experience across x86 and Arm for gaming thanks to the likes of Proton, FEX and other open source projects that Valve fund. We all benefit from it thanks to it all being open source.




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