The Zorro II bus is now arbitrated fairly. The normal slot-based order of precedence is given to requesting devices, just as in the A2000 implementation. As always, once a bus master assumes bus mastership, it has the bus for as long as it wants the bus (of course, trouble can result if a device takes the bus over for too long). Once a master gives up the bus, it will not be granted it back until all subsequent requests have been serviced. Bus arbitration at its best will be slightly slower than in the A2000 implementation, due to the fairness logic, but it is impossible to jam the arbiter with asynchronous bus requests as in the A2000. The new style arbiter also holds off bus grants while hidden local bus cycles are in progress, so there's no guarantee of a minimum time between bus request and bus grant specified.
[Back to Amiga Developer Docs]