I installed my CUDA toolkit by CUDA-5.0(Driver version 5.0 && Runtime Version 5.0) on K20.
For new characteristics, I installed cuda-9.0 tookit nowadays. However, I got a LOWER performance on my project with driver version 9.1 and runtime version 9.1 than before!
Meanwhile, I tried to install driver version 9.1 with runtime version 5.0, but I got a lower performance than before unfortunately.
Why does it happen? Why does the higher version get a lower performance?