FSR 4 modded to run on RDNA 2 GPUs improves image quality by “leaps and bounds,” but carries 10% performance penalty — AMD’s leaked source code turns into modding frenzy

Last month, AMD accidentally made FSR 4 open-source by publishing the entire source code on GitHub, as part of its FidelitySDK. That pushed modders to quickly reverse-engineer how to run FSR 4 on previously incompatible hardware, but the hacks were limited to Linux. That changed just last week when u/AthleteDependent926 on Reddit figured out how to make it work on Windows — we saw a 12-20% decrease in potential performance with it, and today new findings on older RDNA GPUs corroborate our testing.

There are actually three aspects to this story: first, we have an RX 6800 XT that showed a noticeable uptick in visual fidelity at the cost of FPS; secondly, Computer Base tested a bunch of GPUs that saw similar declines in performance; lastly, a Reddit user also tried FSR 4 on their RX 6950 XT and praised its image quality while noting fewer frames achived compared to XeSS. The focal point of the story, though, is the large overhead FSR 4 brings with it, even if it offers a much better-looking image than its predecessor.

User kkrace on Chiphell managed to get FSR 4 running on an RX 6800 XT, which is an RDNA 2 graphics card that lacks the proper hardware needed for FSR 4. As such, they saw only 100-107 FPS in Stellar Blade when using FSR 4, compared to 110+ FPS on FSR 3. Even though that’s only a ~3-10% decrease, the user claims they saw 10-20% worse frame rates; however, the image quality was significantly better. Therefore, they suggest switching to FSR 4 regardless, because, at triple-digit FPS, you might as well take the slight performance hit for majorly upgraded visuals.

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The OP on Chiphell modded FSR 4 onto Stellar Blade — a game that only supports FSR 3 natively — using a tweaked DLL that allowed it to work with OptiScaler. The guide to do that was posted later on Reddit by user u/NaM_77, who listed an older driver as a prerequisite. They tested it using their RX 6950 XT and, while no comparison numbers with FSR 3 were provided, the RX 6950 XT still gained about 10% more frames with FSR 4 when tallied against native (TAA) results. Intel’s XeSS, on the other hand, had even better performance, but the user highlighted that it was unstable and not as good-looking.