Windows 7 displays all CPU cores in Performance tab in Task Manager by default but it’s not the case in Windows 10. When you open Task Manager in Windows 10 and go to Performance tab, here is the CPU usage graph you see by default, an overall utilization of all cores available in the process.
But you can change the view to display all cores if you like. Right-click inside the CPU graph, choose Change graph to and Logical processors.
The CPU graph changes to the way it is in Windows 7, like below.