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