{HEAD ~ controller} means for updating, via non concurrent clock cycles, the associated mirror image data validity status information in said {TAIL ~ first directory} means 
{ HEAD ~ controller } means for updating , via non concurrent clock cycles , the associated mirror image data validity status information in said { TAIL ~ first directory } means
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH