bus interface means for monitoring data moved on said system bus and for sensing via a hardware implemented protocol any modification of {HEAD ~ said moved data} for {TAIL ~ storage} of validity status information in said second directory means 
bus interface means for monitoring data moved on said system bus and for sensing via a hardware implemented protocol any modification of { HEAD ~ said moved data } for { TAIL ~ storage } of validity status information in said second directory means
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH