Motorola developed the MC6839 which allowed one to do floating point math with the MC6809. The MC6839 was not a floating point CPU, but an actual 8K ROM of 680

Motorola developed the MC6839 which allowed one to do floating point math with the MC6809. The MC6839 was not a floating point CPU, but an actual 8K ROM of 6809 machine code that implemented floating point math (with position independent code so it could be mapped anywhere in the memory map). This is about the closest I have ever seen of a "software IC" in my life.