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Credit: AMD
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.
Credit: kkrace on Chiphell
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.
These sentiments are echoed by Computer Base's testing, which didn't use an RDNA 2 GPU. Rather, they pitted an RX 7900 XTX against an RX 9070 XT — AMD's latest flagship purpose-built with FSR 4 in mind. Surprisingly, it still underperformed compared to FSR 3. In Cyberpunk 2077 , tested at 4K Ultra settings, the 9070 XT netted 77 FPS using FSR 3.1 and only 74 FPS using FSR 4. More importantly, though, the RDNA 3-based 7900 XTX saw 16% fewer frames in FSR 4 compared to FSR 3.1, but again justified that with markedly better visuals.
Credit: Future
All of this to say, FSR 4 seems worth it when it comes to delivering solid image quality, though it still demands significant compute regardless of whatever hardware it's running on. Modders were able to tweak FSR 4 to run INT8 libraries, which themselves have a noticeable discrepancy between each other. FP8 support is only available on RDNA 4, similar to how RDNA 2 GPUs need to fall back on slower instructions like DP4a to run FSR 4 (which explains the missing FPS).
It's important to note that AMD is also working on FSR Redstone as we speak; it's the company's next-gen upscaler designed to work on a myriad of GPUs, including non-AMD ones, which is perhaps why the Red Team hasn't extended FSR 4 support beyond the RX 9000 series yet. Though it's clear that if you're dedicated enough, that's not a hurdle — as long as you can live with worse performance in exchange for sharper fidelity .
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