Correction: you can do pre-emptive multi-tasking on z80. I wrote an OS to take advantage of this back in the day. It has interrupts, after all. User programs (a

Correction: you can do pre-emptive multi-tasking on z80. I wrote an OS to take advantage of this back in the day. It has interrupts, after all. User programs (as it were) can disable interrupts, but the z80 has NMIs as well if your hardware configuration is suitable for it.