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the originals ran like 3 'cpu groups' or whatever they called it... all instructions ran on all 3 and the results were compared - one of the cool things done with this was taking faulty 'cpu groups' out of service without down time

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This 'voting' strategy is used a lot in hi-rel aerospace and military computers as well.

And in space. Eg shuttle used 3 main dSpace controllers, instead of hardening the hardware. Still cheaper, and much faster.

'Aerospace' usually covers 'space'. The shuttle used 5 IBM AP-101 flight computers (4 synch'ed voters for the core avionics software, 1 for independently written backup software). The AP-101 was designed to be a hi-rel computer for military use, so it's very much 'hardened' (including EMP protections), but not internally redundant. They were not cheap. Ken Shiriff has several articles about the hardware: https://www.righto.com/2026/03/ibm-4-pi-computer-history.htm...

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