Abstract: A bus guardian unit for a system in which processors, memories and other units are not grouped together physically but where any plurality of identical units e.g., three, can be made to operate in synchronism as though they were grouped together. Each unit would potentially be able to deliver data to any one of a number of buses and each of the three units operating in synchronism would normally deliver data to a different bus. Units accepting data from the bus system use data from three buses to determine the majority consensus of a triplet. The invention also allows idle units to be unpowered until needed either as replacements for failed units or else to provide extra computational capacity for system mission phases requiring same.