Do nonexistent CPUs count? Redcode, used in the CoreWars programming game, has a SPL instruction which boils down to "branch both ways". You end up with two exe

Do nonexistent CPUs count? Redcode, used in the CoreWars programming game, has a SPL instruction which boils down to "branch both ways". You end up with two execution pointers taking turns. One keeps going as if the SPL is a nop. The other keeps going as if the SPL is an unconditional jump. Of course you're not limited to calling this just the once.