Low-tech? Maybe. One, it takes a long time to design and commission a new modern naval vessel, aircraft, or even a tank. A decade or more. So most on-board electronics, including CPUs and displays will be outdated at any given time — somewhat outdated to possibly very old. (Side note: I've always been amazed at how quickly new ship and plane designs came out in war-time in the 1940s, but they were much simpler then and evolving much more rapidly. Can't really compare a P-51 Mustang to an F-22.)

Two, I don't really want the Navy finding bugs in the latest hardware. Better run an older, well-tested CPU than find a reactor control system crashing because of a f00f bug. :)