Fault tolerant memory system which utilizes data from a shadow memory device upon {HEAD ~ the detection} of {TAIL ~ erroneous data} in a main memory device 
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Fault tolerant memory system which utilizes data from a shadow memory device upon { HEAD ~ the detection } of { TAIL ~ erroneous data } in a main memory device
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH