In the 1960's whenever we had a hardware failure on the Dartmouth Time Sharing System the field engineer would run hardware diagnostics to try to locate the problem. He was never successful but after he ran the diagnostics everything worked perfectly.
So every morning he ran hardware diagnostics. If you asked him what he was doing he said he was warding off evil spirits.
On day he was warding off evil spirits the diagnostic stopped on a solid hardware failure. But time sharing worked perfectly. Further inspection showed that the failure was in the "bit change zero" instruction that changed friden flexowriter codes to ascii. It was about the only instruction we didn't use.
Biting the hand that feeds IT
