Comment Re:Hot Rod Z80 (Score 1) 79
My guess would be that 24 bit address space for the MMU, and that this worked better with the Z80.
There were ways to extend the 6809 space by a couple of bits, but not by eight.
The greater abundance of registers on the Z80--including an entire second set of the 8080 registers, which could be toggled between--sounds like a likely reason. IIRC, the 6809 didn't have any extra data registers as compared to the 6800.
hawk