A plane doesn't need flight computers, it just needs control systems that react to inputs. These kinds of systems can be totally mechanical, totally digital, or

A plane doesn't need flight computers, it just needs control systems that react to inputs. These kinds of systems can be totally mechanical, totally digital, or a mixture of both. In the 60's, many of these systems would have been mechanical, with the digital circuitry operating at a higher level to provide the pilots with operational control. You also have to remember that many of the cycles on a modern desktop are wasted, dealing with the gui, and lots of abstraction layers. Most embedded control systems are much simpler, and are closer to the baremetal, so they don't need GHz of computing power.