Mark Cerny says PS5 Pro’s new PSSR uses INT8 (like the leaked FSR4 for RDNA3/2)
© Sony Mark Cerny has now given the clearest description yet of how Sony’s updated PSSR relates to AMD’s latest FSR upscaler. In Digital Foundry’s interview, Cerny said the new PSSR uses the same core co-developed algorithm as FSR Upscaling, but with a different implementation because AMD’s PC version uses FP8 while PSSR on PS5 Pro uses INT8.
On PCs, FSR Upscaling is only for RDNA4
The INT8 version lines up with the unofficial FSR 4 INT8 builds that surfaced last year and were later tested on RDNA 2 and RDNA 3 graphics cards. Those tests showed the INT8 path trailing the official FP8 version on RDNA 4 in both image quality and performance, but still producing better output than FSR 3.1 in many scenes.
“FSR Redstone and the new PSSR have somewhat different implementations due to the underlying hardware, eg FSR Upscaling uses 8-bit floating point and PSSR uses 8-bit integer. The MAC counts (ie the amount of math involved) also vary a bit, and training data is similar but not exactly the same. None of the above factors seem to make too much difference in results; as both SIE and AMD have just released their refreshed models, it will be an excellent test of how closely we can match our systems.”
— Mark Cerny
Sony PlayStation 5 Pro is not pure RDNA4 design. The base technology is still relying on RDNA2, however it implements ray tracing from RDNA4 and machine learning from custom RDNA design (presumably RDNA5).
Source: Sony
While Sony PlayStation adds INT8 version, the latest update for FSR Upscaling (4.1) is only supported on the Radeon RX 9000 series. Older GPUs fall back to the analytical FSR 3 path instead of the neural model.
“In practice, the same model is used but it’s trained on different data, eg 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. Having said that, not seeing too much difference in results, the various flavors in the updated FSR Upscaling really are rather close to the new PSSR.”
— Mark Cerny
Cerny said the training data is similar between FSR Upscaling and PSSR, though not identical, and added that the refreshed FSR Upscaling variants are close to the new PSSR in output. That suggests Sony and AMD are now shipping two closely related versions of the same Project Amethyst upscaling work, one tuned for FP8 on RDNA 4, and one tuned for INT8 on PS5 Pro. This makes us wonder, how hard would it be to implement this INT8-optimized version on RDNA3/2 cards?
Sources: Digital Foundry
