[vidarh]

> was necessary for a Unix-like OS to be created

There are Unix-like OS's on MMU-less architectures. Though of course there are limitations (like not supporting fork(), only vfork()). But you're right that it made it a lot more attractive to try to do a proper Unix.

There were even commercial Unix workstations based on MMU-less CPU's. An example is the Sun 1 workstation, that used an 68000 (Since the first version - the 68000 - is not fully restartable, various hacks were used on 68000 designs requiring an MMU; I'm not sure what the Sun-1 did, but one example that was used was running two of them in lockstep, and have the MMU halt the second one when the first one triggered a page fault, so that it'd be possible to inspect the CPU state before a bus-error would mess it up. From the 68010 onwards this was unnecessary)