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