Hi, I.m referring to a simple MPSMatrixMultiplication performance test code provided in another post: https://developer.apple.com/forums/thread/105534 You can save the code (the 2nd one) in some file, say testMM.swift and compile it from a terminal by executing: swiftc -O testMM.swift Then run the executable in Terminal by executing: ./testMM The code performs a matrix multiplication using MPSMatrixMultiplication and reports the calculation performance of your GPU in GFlops. On my MacPro 2019 with AMD Vega II, I got 3500 GFlops. Now I did this test again by recompiling the exact same code after installation of macOS Big Sur 11.3 and XCode 12.5. The performance dropped down to only 119 GFlops i.e. a dramatic performance loss of more than a factor of 30! Are there any fundamental changes on how to use Metal performance shaders? Any idea?