The Motorola 6809 is an 8-bit microprocessor introduced in 1978.
The 6809 is only compatible to its predecessor (the Motorola 6800) on assembler source level, not in binary programs nor electrically.
Improvements over the 6800 allow position-independent and re-entrant code, 16-bit arithmetic, a hardware multiplication instruction, and a fast interrupt system.
It came in 1 MHz, 1.5 MHz (68A09) and 2 MHz (68B09) speed grades, and initially in 40-pin DIL packages.
- Motorola 6809 @ Wikipedia