How does FSR 4 scaling work on older AMD graphics?

AMD released a new version of its FSR scaling technology this spring, and it was a huge step forward. Technical analyzes rated the new product very highly, because AMD reached a level between the older CNN DLSS model and the newer Transformer, although the previous version of FSR was far behind the CNN model in quality. There was one catch, however: FSR 4 is officially only available for AMD’s latest RDNA 4-architecture graphics, the Radeon RX 9000 series, and that’s because they support FP8 instructions, which the technology uses for computing. But, as it turns out, this is not the only version of FSR 4 in existence.

Previously, there were rumors that the second version of PSSR, an upscaling for the PS5 Pro console, would be based on FSR 4, but even that device does not support FP8, so it will need a slightly inferior version of INT8. And as we recently learned, such a version really exists. When AMD updated the SDK of the entire FidelityFX suite on Github, it accidentally uploaded files related to FSR 4, namely the INT8 version, which could potentially also run on RDNA 3 and 2 architecture graphics. A detailed test of this alternative version of FSR 4.

Firstly, there was the image quality, it is definitely not the same, it depends not only on the architecture, but also on specific drivers. So there are already more artifacts on RDNA 3, and with RDNA 2 the graphics are even a little worse. However, the INT8 version of FSR 4 can be quite close to the FP8 version and at the same time it is much better than FSR 3.

In terms of performance, the Horizon Forbidden West test on the RX 7700 XT (RDNA 3) showed that at 1440p this version of FSR 4 (balanced mode) performs similarly to DP4 and the XeSS version (quality mode, same input resolution as balanced at other scales, see our old article) from Intel and 17% better than native 1440p resolution with TAA, while FSR 3 offered 14% better performance than FSR 4. At 4K there are more differences, with FSR 4 Performance this technology offers 39% more performance than native 4K, a little more XeSS Balanced, but FSR 3 is already 69%, which is already a pretty significant difference.

On RDNA 2 the situation is a little worse. Ledbetter tested the RX 6700 and at 4K FSR 4 in Performance mode offered “only” 28% more performance than native 4K. Compared to FSR 4, XeSS Balanced is 15% faster, and FSR 3 is exactly 29%. At 1440p, FSR 4 Balanced is only 11% better than native QHD, XeSS quality is 20% better, and FSR 3 Balanced is 39% better.

That’s all about the situation in the field of tabletop cards. As it turns out, FSR 4 may have value and is definitely worth a try, but due to the significant drop in performance compared to FSR 3, it may not be the best option. But there will definitely be applications, for example, Ledbetter tested the demanding Survival Horror Alan Wake 2, where, despite the lower input resolution, the FSR 4 Performance offered better image quality than the FSR 2 Balanced, and even additional FPS blocks.

But when it comes to portable devices, where this technology could theoretically be used, the numbers are not very favorable. To achieve a significant performance boost, you’ll have to go for some pretty aggressive scaling, which is already quite noticeable at an output resolution as low as 720p. However, there are exceptions, for example, another game from Remedy, namely Control. With FSR 4, playing on Steam Deck will provide significantly higher performance than the native resolution, allowing you to enjoy the game even with ray tracing.

An interesting fact, by the way, is that FSR 4 in the INT8 version can also be used on RTX graphics from Nvidia. In general, however, you probably won’t have much reason to do this, since all RTX cards support CNN and Transformer DLSS models. However, out of curiosity, Ledbetter tested FSR 4 on the RTX 5060 Ti and the result was not very good, the upscaling there was slower than on a similar card from AMD.

We’ll see when we get the full official version of FSR 4 in INT8 form, as it’s possible that it could be very different from this leak. Real-life usage will also be interesting, since we are talking not only about PCs, but also consoles. As mentioned here, the PlayStation 5 Pro should get the new INT8 FSR 4 based PSSR next year, but potentially the Xbox Series X and S could also support similar technology, they have the hardware for it. On the other hand, the base PS5 is out of luck in this regard, because the INT8 instruction is not supported and will likely remain only with FSR 3.

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