Is a 1989 Cadillac computer and 1993 compatible?

No, a 1989 Cadillac computer and a 1993 Cadillac computer are almost certainly not compatible. Even within the same brand and model of car, Cadillac's computer systems changed significantly year to year in that era. The protocols, connectors, and even the software were different. Trying to install a 1989 computer into a 1993 Cadillac would likely result in the car not starting or running properly, and could potentially damage other components.