If the local CPU addresses a memory module which is different from the last accessed memory module, then the subsystem monitoring circuit initiates {HEAD ~ a request} to maintain {TAIL ~ control} of the system bus 
to maintain
If the local CPU addresses a memory module which is different from the last accessed memory module , then the subsystem monitoring circuit initiates { HEAD ~ a request } to maintain { TAIL ~ control } of the system bus
OTH OTH 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 REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH