This link from wikipedia has pretty much a good laundry list of descriptions different companies have taken for doing lock-stepping, etc https://en.wikipedia.or

This link from wikipedia has pretty much a good laundry list of descriptions different companies have taken for doing lock-stepping, etc https://en.wikipedia.org/wiki/Lockstep_%28computing%29 https://en.wikipedia.org/wiki/Lockstep_%28computing%29 . It's also one of the reasons this level of machine is so expensive. Each mainframe core would be two cores in a "normal" system, plus mainframes have logic to decommission a cpu without needing a shutdown, by migrating the workload to a spare processor.