The HCS12 architecture only has two arithmetic-use registers (a and b), and as such, its instruction set was expanded to remove the need for registers to be specified in the instruction word. Add a to b is a separate instruction from add b to a, rotate a is a separate instruction from rotate b, etc.
it is my backup vehicle. Hard to find a more reliable back up vehicle than a 2001 Toyota 4Runner with 130k miles. I also like driving on trails and going hiking out in the deep woods..