Shortly after AMD released FSR 4, claiming that the tech was exclusive to the latest RDNA 4 GPUs, the company seemingly accidentally published the libraries that make up the backbone of the tech, revealing that there may have been a version of FSR 4 planned for RDNA 3 and RDNA 2 GPUs. While this open-sourced oops was later used by modders to bring support to the aforementioned Radeon RX 7000 and 6000 GPUs, a recent Digital Foundry interview with Sony's Mark Cerny suggests that the INT8 version of FSR 4 may have been a compatibility version of the upscaling tech that would later make an appearance as Upgraded PSSR (or PSSR 2.0) on the PlayStation 5 Pro and its RDNA 2 GPU.

According to Cerny, "FSR Redstone and the new PSSR have somewhat different implementations due to the underlying hardware, e.g. FSR Upscaling uses 8-bit floating point and PSSR uses 8-bit integer." He adds that "in practice, the same model is used, but it's trained on different data, e.g. if targeting a 2:1 fixed upscale then the training data used is just for that upscaling ratio - and that different training results in different parameters...not seeing too much difference in results, the various flavors in the updated FSR Upscaling really are rather close to the new PSSR." He also mentions that, on PC, because players are generally so much closer to their monitors than living room gamers are to their TVs, the goals of FSR and PSSR differ slightly.