An arbitration method and mechanism assigning {TAIL ~ priority} to one of {HEAD ~ a combination} of requesters 
An arbitration method and mechanism assigning { TAIL ~ priority } to one of { HEAD ~ a combination } of requesters
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH