 Unlike the 6800 and 6502, the 6809 allows fully position-independent code and fully reentrant code in a simple and straightforward way.It was one of the first microprocessors with a hardware multiplication instruction, and it includes full 16-bit arithmetic and a fast interrupt system.Among the significant enhancements introduced in the 6809 are the use of two 8-bit accumulators (A and B, which can be combined into a single 16-bit register, D), two 16-bit index registers (X, Y) and two 16-bit stack pointers.