[vidarh]

The only thing you need to achieve pre-emptive multitasking is interrupts and the ability to cleanly save the current CPU state.

The 68k lacked the ability to resume with full state intact after a bus fault, which made an off-chip MMU painful (but there was one - the MC68451[1]), but this doesn't affect the ability to do pre-emptive multitasking at all.

AmigaOS famously did have preemptive multitasking - we used it to mock PC and Mac users with for years.

[1] https://en.wikipedia.org/wiki/Motorola_68451 Note that to do full virtual memory with a 68k, Motorola proposed using a second 68k to handle page faults due to a design flaw:

https://retrocomputingforum.com/t/correcting-errors-by-dupli...

[steve1977]

There were also alternatives to the Atari ST TOS which feature preemptive multitasking, like

https://en.m.wikipedia.org/wiki/MagiC

and

https://en.m.wikipedia.org/wiki/MiNT