"What about implementing an algorithm in 3 similar micros (preferably each from a different manufacturer to avoid repeatable manufacturer-created bugs) and pass each output through a "voting gate" of (A&B)|(A&C)|(B&C) "

At the very least such a setup could be designer's nightmare to implement ;-)

Such triple redundant systems are not new anyway - I have physically seen such systems in AeroSpace applications, in a launch facility that is close to my place. Not only on board rockets, but also on ground support systems.

For instance, the computer handling the filling of earth storable liquid propellant into rocket engines is one such TMR ( Triple Module Redundant) system that I have seen.Three monitors, three CPUs and three keyboards. And you know what ? The keyboards are dual sided - and pivoted. If the top keypad fails, you just turn the keyboard on its pivots and type away as if nothing happened!! Some redundancy that....


Raghu