One day I should finish my CP/M emulator for an MSP430 microcontroller with 2kB of ram (swapping out to external storage to emulate the CP/M 64kB address space). I got it up to the point of providing a login prompt --- it'd boot in about 10-15 seconds. You could type on it via a external PC/XT keyboard (bitbanged through the GPIO pins!), but I never got the screen to work, or any proper mass storage for disk. (The 8080 architecture is surprisingly elegant and orthogonal. The Z80's a bit of a mess by comparison.)

...what? Why are you looking at me like that?