While AMD's shiny new FSR 4 is ostensibly exclusive to Radeon RX 9000 series, there have been a number of successful attempts to get it running on older AMD Radeon GPUs after a rather sizeable mistake on AMD's part led to the FSR 4 libraries leaking online. Now, however, a Linux developer working for Valve has implemented a fix to get FSR 4 running on older GPUs right into the Proton translation layer responsible for running Direct3D 12 via the Vulkan API on Linux. Support for FSR 4 is only one of a bunch of updates to D3VK-Proton shipping in the latest 3.0 update.

As of version 3.0 of VKD3D-Proton, the translation layer responsible FSR 4 is present for RX 9000 series Radeon GPUs using the official method, but the Valve developer behind the project, Hans-Kristian Arntzen, has also implemented a "hacky emulation path" that allows FSR 4 to work on older Radeon GPUs. The developer notes that this implementation uses int8 and float16 cooperative matrix support, and that it may come at "significant performance cost." It is, as such, not officially supported by the default build of VKD3D-Proton, and the current official implementation is also mostly a first step in the process of getting FSR 4 implemented "in a more proper way" into Valve's Proton itself. Support for FSR 4 may not be relevant to devices like the Steam Deck, due to the increased performance hit, but it may become more important around the release of the Steam Machine, which still relies on RDNA 3 GPU cores but is expected to provide around the same performance as an AMD Radeon RX 7600M.
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