On a Macintosh computer that does NOT support hyperthreading (e.g. an iMac 5K with an intel i5 CPU) the main CPUSetter window will look something like the one shown above. If the CPU does have support for hyperthreading an additional check box will be shown that lets you enable or disable hyperthreading.
To alter the number of active cores, you must first be authorised by clicking the padlock icon and entering an administrator name and password when prompted.
The number of active cores is adjusted by either using the numeric control or slider.
Clicking on the ‘gears’ icon will open the Processes window where you can adjust the cpu usage of individual processes.
Clicking the ‘Activity Monitor’ icon will launch the macOS system utility of that name.