The control "computer" for the engines of the SR-71 is hydraulic, not electronic. Some of the parts of this aircraft reach temperatures beyond what current semiconductors can cope with.

If you watch a YouTube on the J-58 engines that go into this plane, you will find out that it behaves like a jet at "low" speed (like Mach 1 or below) while at Mach 3 it behaves like a ramjet. There's no other aircraft engine that does this.