CPU frequency support
To enable CPU Frequency monitoring in iStat Menus, please download and install Intel Power Gadget, then restart your Mac.
Intel Power Gadget 3.5.1 is causing significant issues for some customers running macOS 10.13.4. We do not yet know which Mac models are affected, and we have not been able to reproduce the issue. Please install with caution, until Intel releases an update. The comments on the Intel Power Gadet page provide a little more info, but not much.
Download Intel Power Gadget