{HEAD ~ Hardware} implemented {TAIL ~ cache coherency protocol} with duplicated distributed directories for high performance multiprocessors 
implemented
{ HEAD ~ Hardware } implemented { TAIL ~ cache coherency protocol } with duplicated distributed directories for high performance multiprocessors
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH