CUDA Driver Version = 9.0, CUDA Runtime Version = 8.0

Hello there, I am trying to install CUDA 8.0 on Ubuntu 16.04, like,

sudo apt-get install cuda-8-0
cd /usr/local/cuda-8.0/samples/1_Utilities/deviceQuery
sudo make

and the result is:
deviceQuery, CUDA Driver = CUDART, CUDA Driver Version = 9.0, CUDA Runtime Version = 8.0, NumDevs = 1, Device0 = GeForce GTX 970
Result = PASS

Driver Version: 384.130

why the CUDA Driver Version and Runtime Version are different?

because the API level supported by the CUDA driver (384.130) is up through CUDA 9.0. Kind of like saying you can use that CUDA driver with any installed CUDA version up through CUDA 9.0.

But the actual installed CUDA version you have is CUDA 8.0, so that is reported as the CUDA runtime version.

More specifically, the CUDA driver supports a particular CUDA (driver and runtime) API version. That is CUDA 9.0

The installed CUDA runtime is CUDA 8.0

Thanks a lot!