{HEAD ~ All requests} for {TAIL ~ a cache line} are screened by the blocker associated with each home directory 
for
{ HEAD ~ All requests } for { TAIL ~ a cache line } are screened by the blocker associated with each home directory
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH