Each processor has its own cache directory and {HEAD ~ image directory} that duplicate {TAIL ~ each other non} atomically 
Each processor has its own cache directory and { HEAD ~ image directory } that duplicate { TAIL ~ each other non } atomically
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH