Pytorch installation requires cuda toolkit which already installed

Hi, I tried to install pytorch for Python 3.5 and Cuda 8.0. I already installed cuda. However, when I installed pytorch using the command conda install pytorch torchvision -c pytorch, there were some required packages including cudatoolkit: 8.0-3 and the process is very slow compared to the installation process before.

Anyone knows the reason why the cudatoolkit is required when it’s already installed in the machine and what makes the process slow down?

Thank you in advance.