[yuhong]

Another cost of the "more elaborate microcode" is that there was no way to resume or restart execution of the current instruction after a bus error exception. The 68010 fixed that by dumping internal state onto the stack. I wished that after 68010 was released that Motorola promoted the 68010 for new development and the original 68000 only for situations where the system software cannot be modified (since to fix the problem the exception stack frames had to be changed). Motorola had some patents describing how it worked: https://www.google.com/patents/US4493035

[ajross]

This is true, but the '10 wasn't released until the Mac was well into development (and the Lisa was nearing release). Motorola sort of missed the window there. And in any case no 68k Macs would ever end up making significant use of an MMU anyway. By the time that became possible the platform had moved on to 68020/30 parts.

Obviously all the Unix vendors jumped on the '10 instantly. The MK68000 itself was never dominant there.

[yuhong]

Yes, but the 68010 is pin compatible with the 68000 at the hardware level and the software changes are trivial.