Valve has begun integrating AMD's FSR Upscaler 4.1 into its Proton compatibility layer to enable FSR 4.1 on the SteamOS Linux-based operating system. Recently, we reported that AMD has been developing a separate model for FSR Upscaling 4.1 to function on RDNA 3. This involves converting from the FP8 data type used on RDNA 4 GPUs to INT8 data types to ensure smooth operation on RDNA 3. One of the biggest questions surrounding FSR 4.1 compatibility was whether the solution would work with RDNA 3.5 integrated graphics, in addition to the already announced RDNA 3 IP support. Valve has now leaked the FSR 4.1 INT8 model, which has been observed running on RDNA 3.5 thought Radeon 890M GPU.

Valve has included preliminary FSR 4.1 support in its Proton Experimental build, which is used for testing features before they appear in the stable release that ships with SteamOS builds. A Redditor managed to download the leaked file before Valve removed it and ran a few tests using OptiScaler to force different FSR DLL versions in games. Since the file is officially signed, games checking for DLL signatures reportedly ran without issues. This is great news for those waiting for the official DLL release, especially RDNA 3.5 users who were left uncertain about whether FSR 4.1 would work with RDNA 3.5.

Finally, we understand that there are some fundamental differences in the RDNA generations regarding microarchitecture. For RDNA 3, there is no support for 8-bit floating point, as only the latest RDNA 4 uses FP8. To run the FSR 4.1 Upscaling model on RDNA 3, AMD must convert it to 8-bit integer data, as RDNA 3 hardware uses INT8 data types without FP8 support. Generally, integer math is sufficient to optimize these models, but the conversion work is necessary, which explains the delay between RDNA 4 and RDNA 3 support. However, since RDNA 3.5 appears to be closer to pure RDNA 3 with its data types support than RDNA 4, running the INT8 model of FSR 4.1 without any problems seems to be a good sign that the official support will be there.