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.