>VAX and 68000 ABIs sadly and (really, unnecessarily) used the stack, leaving a lot of performance on the table. AmigaOS uses registers for parameter passing o

>VAX and 68000 ABIs sadly and (really, unnecessarily) used the stack, leaving a lot of performance on the table. AmigaOS uses registers for parameter passing on m68k. a0/a1 and d0/d1 are scratch (and also the first to be used to pass or return pointers or values). The rest you're meant to preserve. Atari TOS (probably inherited from CP/M for m68k) unfortunately uses the stack.