There are very few functional requirements on that kind of a system that are linearly improved by a faster computer - it's not like they're mining bitcoins in f

There are very few functional requirements on that kind of a system that are linearly improved by a faster computer - it's not like they're mining bitcoins in flight. "Doing X in real time" is usually the goal and any faster is superfluous. OTOH, "X percent more robust when pulling G's / subjected to EMP / hit by shockwave" is an excellent property to have, so you stick with simpler systems.