Motorola 6809 was a great improvement over Zilog Z80 (previously the best "8-bit" processor), but unfortunately it was introduced too late, in 1979, when the transition towards 16-bit CPUs able to address more than 64 kB of memory had already started.

Motorola had made the mistake of introducing at the same time 2 different incompatible ISAs, one for CPUs covering the low-end of the market, MC6809, and one for CPUs covering the high-end of the market, MC68000. This mistake has cost them the chance of being selected for the IBM PC (because MC68000 was considered too expensive, while MC6809 was not future-proof, with its limited addressing space). After they have seen the success of Intel with its 2 software-compatible CPUs, 8086 for the high end and 8088 for the low end, Motorola has also introduced MC68008, a MC68000 variant for cheaper computers, but it was too late, as the IBM PC became dominant.