While FSR 4 can run on RDNA 2 / RDNA 3 GPUs and bring real visual progress, performance falls off quite a bit.
At the time of its release, AMD's FidelityFX Super Resolution 4 (FSR 4) technology was to be reserved for RDNA 4 architecture graphics cards only, just as NVIDIA limits DLSS 4 to its GeForce RTX 50 series only. In either case, previous generations of cards would not be sufficiently equipped to run such technologies. The reality of things is a little more complicated, at least on AMD's side.
Thanks to a modified DLL and OptiScaler, FSR 4 runs on Radeon RX 7900 XTX. Here, Cyberpunk 2077 © Reddit
A few weeks ago, to help developers in their work around FSR 4, AMD released what is known as an SDK of its latest technology. The tool was placed on AMD's GitHub repository, but a mistake was made. In fact, too many files were made available, and some people realized that the FSR 4 source code was among the elements available. AMD was even slow to correct its error, but even if it had reacted quickly, the damage had been done. The source code was thus "out there", and soon fell into the hands of clever souls who set about working on it.
Better still, it also runs on Radeon RX 6800 XT. Here, the Stellar Blade example © Chiphell
The aim was to come up with a modified FSR 4 library (DLL) that would run on architectures older than RDNA 4. Don't think the thing works on its own, but by replacing FP8 calls - which only RDNA 4 cards can exploit - with INT8 instructions, it is indeed possible to run the thing on RDNA 3 and even RDNA 2. This also requires the use of OptiScaler software, but a game like Cyberpunk 2077 then renders better: FSR 4 corrects many of FSR 3's visual shortcomings, albeit with a loss of performance. On a Radeon RX 7900 XTX with 1440p graphics details at maximum, the loss would be 6 to 7 frames per second. Nothing dramatic.
FSR Redstone: the next step for AMD © AMD
Logically, this loss is a little greater on Radeon RX 6800 XT, an RDNA 2 card. Here, a gamer tried his hand at Stellar Blade. As with Cyberpunk 2077, he noted a more accomplished graphical rendering, but was forced to make do with a loss of around 15 frames per second. On average, on this powerful RDNA 2 card, you have to make do with a drop of between 10 and 20%. That said, several gamers also pointed out that the thing was sometimes unstable and, on The Last of Us 2 for example, it wouldn't be possible to play comfortably because of crashes. This no doubt goes some way to explaining why AMD didn't do more work on this. Another reason may lie in the future of FSR: the next step is called Redstone, and AMD is said to have the idea of porting its technology to more GPUs - notably those of rival brands - it remains to be seen whether earlier ranges will also be concerned.
