Agner`s CPU blog

I have tested the new libraries and found that the CPU dispatching works basically the same way as before. The standard math library, vector math library, short vector math library and the 64-bit version of other math kernel library functions still use an inferior code path for non-Intel processors.

I have found the following differences from previous versions:

• Many functions now have a branch for the forthcoming AVX instruction set, but still only for Intel processors. This will increase the difference in performance between Intel and AMD processors on these functions. Both Intel and AMD are planning to support AVX in 2011.
   
• The CPU dispatcher for the vector math library has a new branch for non-Intel processors with SSE2. Unlike the generic branch, the new non-Intel SSE2 branch is used only on non-Intel processors, and it is inferior in many cases to the branch used by Intel processors with the same instruction set. The non-Intel SSE2 branch is implemented in the 32-bit Windows version and the 32-bit Linux version, but not in the 64-bit versions of the library.
   
• A new Summary Statistics library uses the same CPU dispatcher as the vector math library.

Obviously, I haven't tested all functions in the library. There may be more differences that I haven't discovered. But it is clear that many functions in the new version of the library still cripples performance on non-Intel processors. I don't understand how they can do this without violating the legal settlement with AMD.