The data bus grant line to the memory controller is overloaded to use it as a back pressure, get off the bus signal as well as {HEAD ~ a normal data bus} grant {TAIL ~ line} 
The data bus grant line to the memory controller is overloaded to use it as a back pressure , get off the bus signal as well as { HEAD ~ a normal data bus } grant { TAIL ~ line }
OTH OTH OTH 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 HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL