Why does OC rendering take up CPU?

[JasonKaKa]

I have been studying the material of OC recently. A shader model was downloaded from the web(Do I need to provide the model? I am not sure if it is legal.).
Add a material to the model and click the render button,and the CPU load will instantly reach 100% and last for about 10s and the computer will be particularly slow.
I don't know if someone has encountered such a problem?
I use the GTX1070 and I7 6700K. WIN10 system.
By the way, how do I add a signature? I can't find the place to add.

[paride4331]

Hi JasonKaKa,
it's normal, your cpu core works to process the scene and send it to GPU.
Regards
Paride