"CUDA cores" is a misleading term.

When they quote "CUDA cores", they've been counting float32 fma functional units; e.g., Tesla K40 has 192 float32 fma units per SM x 15 SMs => 2880 "CUDA cores".

http://docs.nvidia.com/cuda/cuda-c-programming-guide/index.h...

fp16 and fp64 are likely different functional units with different issue rates, as is the case with old hardware; unless they've managed to share the same hardware (since for P100 the quoted fp64 rate is exactly half the fp32 rate, and the fp16 is exactly double the fp32 rate).