When NVIDIA and AMD launched their most recent graphics cards, they both came with features only available with the latest hardware.
In NVIDIA's case, that meant that DLSS 4's Multi Frame Generation was only available on RTX 5000 cards, while Enhanced Frame Generation only made it back to 40-series hardware.
For AMD, it meant that FidelityFX Super Resolution (FSR) 4.0 was only available for RDNA 4 GPUs, including the flagship Radeon RX 9070 XT. Those with an RDNA 3 GPU or older were out of luck.
Well, that just changed thanks to the hard work of some enthusiastic Radeon owners and a leaked set of Int8 files used for FSR (via Wccftech).
This all began when AMD accidentally released the entire source code for FSR 4 on GitHub last month. The blunder was quickly discovered and nabbed by savvy users, and until now, the story has mostly been cold.
That is, until posts recently began popping up on the Radeon subreddit containing proof that FSR 4 was running on GPUs that it technically shouldn't run on.
Reddit user AthleteDependent926 created the post that kicked off a lot of experimentation, and it's causing a lot of excitement amongst AMD Radeon GPU owners.
How is AMD's FSR 4 running on old GPUs that don't technically support it?
AMD's FSR 4 is currently officially limited to the latest RDNA 4 GPUs due to their FP8 support. The lack of FP8 support on RDNA 3 (and older) cards was a major block unless a user was running Linux, where it could be forced; Windows users were left out completely.
AMD's accidental GitHub leak contained files that allowed savvy users to compile their own DLL for FSR 4.
Rather than using FP8, a custom FSR 4 DLL using Int8 files was produced, making it compatible with RDNA 2 and 3 GPUs as well as some NVIDIA RTX 30-series cards. Windows users, by employing Optiscaler (which is a handy way to replace upscalers in games), have reported success in replacing FSR 3.1 with FSR 4.
The results I've found on Reddit are quite impressive, although running FSR 4 on older cards isn't perfect. As AthleteDependent926 explains:
The image quality of this Int8 version is substantially superior to FSR 3.1, and also resolves hair and distant detail better than XeSS (which is also an Int8 model). The only downside is that it can be expensive to run, taking up almost triple the processing power of FSR 3.1 on RDNA 3 (0.6ms vs 1.9ms), and quadruple the processing power of Transformer DLSS on an RTX 3060 Ti.
Reddit user nuubcake11 followed up the original post with some testing in Cyberpunk 2077.
Running the game on an AMD Radeon RX 7900 XTX of the RDNA 3 generation with FSR 4 enabled "is working via Optiscaler."
With FSR 3.1.5 enabled, the user saw roughly 84 FPS at 1440p with all settings maxed and ray tracing enabled. Switching to the custom version of FSR 4, frame rates dropped to about 79 FPS.
Losing single-digit frames seems to be a common experience, but users seem to be happy with the tradeoff. FSR 4 removes most of the shimmering in small details.
Another gamer tried Cyberpunk 2077 on an RX 6800 XT from the RDNA 2 generation using CachyOS and FSR 4. As they noted, FSR 4 was able to "come out superior" with sharper images, although performance was a bit weird.
RDNA 2 hardware seems to add some ghosting issues when running on Windows, so it seems like RDNA 3 is still the best way to go if you don't have one of the latest RDNA 4 cards.
What exactly is AMD's FidelityFX Super Resolution?
FSR is AMD's answer to NVIDIA's DLSS, in that it upscales graphics and adds frame generation capabilities.
While AMD relied on advanced spatial upscaling algorithms for versions up to FSR 3, FSR 4 made the jump to machine learning.
This change has contributed greatly to FSR's abilities, and FSR 4 is indeed a big improvement compared to FSR 3. You can see in the video below how much of a difference there is.
AMD has not officially announced that it's bringing FSR 4 to its older AMD Radeon hardware, and that makes sense considering the performance tradeoffs that most users are seeing with this unofficial port.
Whether or not AMD takes a different stance now that this unofficial FSR 4 workaround is out in the wild, I guess we'll have to wait and see.
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