A computing system uses a system busy signal (SDBUSY) on its system bus to help control access to the bus. Each requester requiring access to the bus generates its internal request signal (SET REQ). One or more requesters can generate a request signal (SDREQX) on the bus when the system busy signal is not asserted (gate 74 and flip-flop 76). System busy is asserted along with the request signal(s) and remains asserted until all requesters which generated a request signal have gained access to the bus in order of priority. Bus access is enabled by a signal (PRIORITY) only when all higher priority request signals (SDREQ1-SDREQX-1) are false (gate 72). A freeze signal (DRVFREZ) is generated on the system bus during the address phase of an instruction and a wait signal is generated during each data transfer in the data phase of an instruction. These signals must be false before a requester with its request signal and priority signal tone can access the bus by putting an address signal thereon. The freeze signal may be generated by a memory control unit, a memory module or a requester.