AMD’s Radeon RX 7900 series GPUs may suffer from a buggy mesh shader implementation. The 7900 XT performs worse than both the RX 6800 XT and the RTX 3080 Ti in the 3DMark Shader benchmark. The RDNA 3 flagships gain a modest 30% gain with mesh shaders switched on, going from 165 FPS to 216 FPS thanks to the unified shader pipeline.
This may seem like a large uplift in shader performance, but the GPU ends up slower than every present and last-generation high-end offering, including the RTX 3080, RTX 3080 Ti, and RTX 3090, as well as the RDNA 2-based RX 6800 XT and the 6900 XT. This issue was originally highlighted by @Digidi20 on Twitter, one of the members of the 3DCenter team. We’ve reached out to AMD on the matter and will post an update as soon as we get a response.
At @3DCenter_org we run some benchmarks. N31 behaves strangely. Mesh Shader seems broken on AMD Hardware, you can not start it, also MultiDrawIndirect stays behind the claimed 2,3 Uplift. 1/2
Also, you see that compute shader emulation of the rasterizer is not scaling with the shader power. Also, here you can find that something is wrong with the Mesh Shader:
It is wild guessing, but for me, it looks like AMD has an issue in the front end. The automatic scheduling of the workload to the shader looks broken.
Originally tweeted by Digidi (@Digidi20) on December 18, 2022.