Leaked AMD FSR 4 INT8 Mod Tested on Older GPUs
It has been tested on GPUs from non-RDNA 4 with a hacked version of INT8 AMD FSR 4 based on source code leak. An old piece of hardware has been found to test a modified version of AMD FSR 4 with an INT8 format, following the source code leak. The official version of FSR 4 that was launched along with Radeon RX 9000 (RDNA 4) series is configured using FP8 format, which is unsupported by older generation GPUs. However, the leaked INT8 version is compatible with a wider coverage area, including RDNA 2 and RDNA 3 GPUs. Digital Foundry analyzed this mod for performance and image quality.
Image Quality Comparison INT8 vs. FP8
There are significant differences in direct contrast between the official FSR 4 (FP8) on RDNA 4 hardware and the leaked INT8 version on older GPUs. The INT8 mod is even more susceptible to easily noticeable issues with aliasing and temporal artifacts. These kinds of visual issues have been reported to be especially harsh against AMD's latest Adrenalin 25.9.1 driver; this suggests it could be a bug. Therefore, for users who will be experiencing this problem after testing the mod, downgrading back to the 23.9.1 driver is probably the best course of action to take.
In spite of these artifacts, the analysis certifies that the FSR 4 INT8 version still outdoes the older AMD FSR 3 in terms of upscaling quality.
Performance Analysis and Benchmarks
The major disadvantage of the FSR 4 INT8 mod is its underwhelming performance. Digital Foundry then proceeded to run tests, intended to represent what the upscaler might perform like on an Xbox Series X (which supports INT8) by running those tests with an RX 6700 GPU.
Horizon Forbidden West Benchmark
FSR 4 INT8 proved the slowest upscaler tested in the Horizon Forbidden West benchmark:
- FSR 4 INT8 provided a performance uplift of 28% over native 4K Viewed in Performance Mode.
- Intel XeSS (Balance Mode) was 15% faster than FSR 4 INT8.
- AMD FSR 3 (Performance Mode) was 29% faster than FSR 4 INT8.
Alan Wake 2 Benchmark
A completely opposite finding can be found in Alan Wake 2 at a similar configuration to Xbox Series X at 1440p:
- Here, comparing FSR 4 (Performance Mode) against FSR 2 (Balance Mode), the performance of the FSR 4 mod was improved slightly, yielding a few more frames (about 4%).
- Most importantly, it produced a much cleaner image, albeit reconstructed from a lower internal resolution than that of FSR 2.
Conclusion
While the leaked FSR 4 INT8 mod results in a significant uplift in image quality over FSR 3, it comes with a very steep price in terms of performance when compared to other upscalers. Nevertheless, it can sometimes give a better trade-off in frame rates versus visual clarity compared to older technologies like FSR 2.
