A cpu (core) executes one process at a time. There is a lot of cpu (core) global state that gets saved / restored upon context switch (either between processes

A cpu (core) executes one process at a time. There is a lot of cpu (core) global state that gets saved / restored upon context switch (either between processes or just between user mode and kernel mode). As a side note, there is a often a bit of terminology confusion on whether a cpu is the "die" or the "core". When discussing microarchitecture core == cpu in most cases