You sound like a veteran, so I'm sure you know this and made a typo, but anyway please let me clarify: the 6502 (and Z80, 8080 etc mentioned here) are not micro

You sound like a veteran, so I'm sure you know this and made a typo, but anyway please let me clarify: the 6502 (and Z80, 8080 etc mentioned here) are not microcontrollers. They are microprocessors. Microcontrollers generally integrate more of the things that the are needed in order to build a computer from a "naked" processor, into the same chip. Modern microcontrollers almost always contain onboard flash memory for code and data storage, as well as SRAM and peripherals. A 6502 has none of that, and you need many more additional chips on the board to make it into a functional computer.