What they do in IBM zSeries is they compare the instruction executions on two cores, if they agree. If they disagree, they will retry the operation. If they dis

What they do in IBM zSeries is they compare the instruction executions on two cores, if they agree. If they disagree, they will retry the operation. If they disagree again, they will take the CPU (both cores) offline (and probably call home to IBM to bring a replacement).