The modern microprocessors I've dealt with could have 2 modes: User and superuser (and sometimes this difference was just in the manual and not actually implemented like with the Nios II which states that it has 2 modes but only implements 1). Therefore I wonder if this is true in general about microprocessors i.e. it is not very advantageous to add more modes than 2 for instance a third mode that could be "supersuperuser" (which in practice could be that a "supersuperuser" could change the privileges of "superusers") if there could be need for 3 modes? And is it this mode difference of the CPU in modern systems that has caused the design difference between operating systems where some operating systems are called "microkernels" because of their way to load device driver programs in user mode instead of in superuser mode, which is the way of a monolithic os kernel? What is the history about the 2 CPU modes getting developed? It says in another SE comment:
I saw the names "user mode" and "supervisor mode" in ARM2 first (late 1980's),
So the early microprocessors like Intel 8080 and Zilog Z80 didn't have modes so any program that was run could run any instruction?
Are these 2 modes usually implemented in hardware and if so, what does the implementation look like? What is it that changes when a microprocessor switches modes between user and superuser?