> E.g. we can build a board around a MC68000 where we make it lock up forever in a bus cycle, waiting for a DTACK that doesn't arrive. IIRC, early 68k Macs had

> E.g. we can build a board around a MC68000 where we make it lock up forever in a bus cycle, waiting for a DTACK that doesn't arrive. IIRC, early 68k Macs had processor upgrades hooked onto the 68k bus and did exactly this - an early boot driver run by the “actual” CPU coordinated handoff with the expansion CPU’s bootstrap ROM.