Sure, there are the gui task-managers, but I missed HTOP for simple hardware checking, like making sure all my cores are running. Especially in years past when I had to mess around with acpi-cheatcodes to get Atom cpu's running properly. Like a cheatcode fixing a problem, but dropping down to only one core!

So, in a terminal run top.
To see ALL your cores: Press #1
To see the speed graphically: press lowercase t
To see memory usage grahically: press lowercase m
Get toggly! switch between solid bars to divided line by tapping "t" or "m" more than once. Or a single cpu by toggling 1. Find a combo you like. Resize the terminal if you like.
All these years!! I'll never need to download HTOP again, since this display most of what I need when investigating new hardware or making sure cheatcodes don't fix problems, but cause another like dropping down to only 1 core!