KeyShot is 100% CPU powered and it will use 100% of your computer cores. The more processor cores, the faster the render engine. Although there is no way for the software to adjust CPU usage automatically, you can manually change the number of cores used with the CPU Usage drop-down in the Ribbon.
For more information please refer to the KeyShot Manual (https://luxion.atlassian.net/wiki/spaces/K8M/pages/311918834/Ribbon).