Key Takeaways
1. AMD accidentally exposed the full FSR 4 libraries and source code on GitHub, which were quickly removed but noted by modders.
2. The leaked files included an INT8 version of FSR 4 that works on older RDNA 2 and RDNA 3 GPUs, though AMD has no plans to officially support it for older Radeon cards.
3. The INT8 version of FSR 4 is being used by Sony in the PS5 and PS5 Pro under the name “upgraded PSSR” upscaling solution.
4. There are technical differences between FSR 4 and Sony’s PSSR 2.0, with different implementations due to hardware specifications despite similar core technology.
5. AMD has not commented on the leak, and the only guaranteed access to official FSR 4 support appears to be through the new RX 9000 series GPUs.
AMD recently made a significant error by unintentionally exposing the full FSR 4 libraries and source code on its GitHub repository through the AMD OpenGPU Project. Although the company quickly removed the files, modders had already taken note of the leak.
INT8 Version of FSR 4
The leaked files included details about an INT8 version of FSR 4, which is a lighter version capable of running on older RDNA 2 and RDNA 3 GPUs. Currently, AMD has no plans to launch FSR 4 for older Radeon cards. Interestingly, both the PS5 and PS5 Pro, which utilize RDNA 2 architecture, are operating with an INT8 version of FSR 4, referred to by Sony as its “upgraded PSSR” upscaling solution.
Context of FSR 4
When AMD initially presented FSR 4, also known as FSR Redstone, the company highlighted that it was specifically tailored for its newest RDNA 4 GPUs found in the Radeon RX 9000 series. The GitHub leak reveals that the lighter INT8 version of FSR 4 can function well on RDNA 2 and RDNA 3 GPUs, leaving users with RX 6000 and RX 7000 series without access to this technology.
Despite this, modders quickly downloaded the libraries before AMD could take them down and have started modifying their games to integrate the INT8 FSR 4 build into RX 6000 and RX 7000 series GPUs.
PSSR 2.0 Rollout
Sony has implemented and rolled out an upgraded version of PSSR, which is being dubbed PSSR 2.0, in the game Resident Evil: Requiem. In a recent chat, PlayStation’s lead system architect, Mark Cerny, spoke with Digital Foundry about how the new PSSR technology connects back to AMD.
Cerny elaborated on the technical distinctions between FSR 4 and the new PSSR, stating, “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.”
Core Technology
He added that while the fundamental technology remains consistent, the training process is tailored to each platform, like PC and PlayStation 5. Cerny mentioned, “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 upsampling ratio, and that different training results in different parameters… Not seeing too much difference in the results, the various flavors in the updated FSR Upscaling really are rather close to the new PSSR.”
This provides pretty much confirmation that PSSR 2.0 on the PS5 Pro is effectively utilizing the INT8 version of FSR 4 that AMD inadvertently exposed in its GitHub libraries. To add to the issue, AMD has not commented on the situation, and it appears that Team Red will not offer FSR 4 for older Radeon GPUs, making the purchase of an RX 9000 series GPU likely the only guaranteed way to access official FSR 4 support from AMD.
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