On an 8 bit bus the 68k is almost useless. I am currently working on a project that involves that and looking at the logic analyzer trace is just tear-inducing.

On an 8 bit bus the 68k is almost useless. I am currently working on a project that involves that and looking at the logic analyzer trace is just tear-inducing. 68k has a terrible IPC to start with, and sticking it on a narrow bus cuts it by more than half. You’d be lucky to squeeze 0.8MIPS out of a 16MHz 68k on a 8 wide bus. Mainly the cause is the fact that the smallest possible instruction is 2 bytes. And it will take at least 4 cycles to fetch it (68k will execute a compete nCS cycle PER BYTE - no bursts to be found here).