What is the Mac actually doing right now? To find out, macOS comes with a tool called Activity Monitor. It shows in dynamic tables what the Apple hardware is currently busy with and to what extent. Processes appear in (at least) five tabs in a ranking list that updates every second. By default, the utility starts in the CPU tab, and in it the first column called “% CPU” is selected. But the number displayed there can cause more confusion than help, explains Howard Oakley in a blog post about processor utilization in modern Macs. With the introduction of multi-core processors, which took place over a quarter of a century ago, the “% CPU” specification lost some of its universality: a value of 100 percent simply signals that a single processor core is fully utilized. Values of 400, 800, 2400 percent are therefore by no means impossible on current Macs, but rather unproblematic depending on the equipment. With Intel Macs, there is another factor that reduces the significance of the percentage value: If the processor supports hyperthreading, each core counts twice. This is also reflected in the additional view “CPU utilization history”: more cores appear here than are officially available.
With hyperthreading-capable Intel processors, the activity display assumes that there are twice the number of cores.
No distinction based on frequency
In Apple silicon processors, the differentiation of the computing cores further reduces the significance of the percentage values: efficiency and performance cores work at different frequencies. In Pro, Max and Ultra versions, groups of performance cores can also run different frequencies. On top of that, the system adjusts dynamically – core groups dynamically change the clock rate as needed. The Activity Monitor does not take these differences into account when displaying the CPU percentage display.
Note other columns
If you are looking for a real performance brake, you should not rely on the percentage CPU utilization, but take other factors into account, such as the number of threads, says Oakley. If an app no longer responds and the spinning ball appears, this is usually not due to a fully utilized CPU, but simply to a process in the app that is no longer responding.
More information via terminal
If you want more detailed values for the utilization of individual Mac computing units, you can’t avoid the terminal at the moment. The “Powermetrics” tool is part of macOS and can be accessed from the terminal; it logs extensive status values from the CPU, GPU and NPU for a given moment, including the current clock speed. However, the resulting numerical values, recorded over a long period of time, can hardly be recorded and analyzed without the help of a computer. Anyone who uses the Homebrew package manager can install a command line visualizer on Apple Silicon Macs using the “brew install asitop” command. This can then be done with the command
sudo asitop
and then entering the admin password. In addition to the current load and frequency of E, P and GPU cores, this display also breaks down the activity of the neural nuclei – these are completely left out of the activity display. In combination with the activity display, this creates a more complete picture. However, the command line tool has not been updated in three years and no longer displays correct values on newer Macs.
The command line tool “asitop” provides a graphical overview of the current utilization of the various computing cores of an M1 processor.
