Fair arbitration scheme for arbitrating between multiple nodes in a computer system seeking control of a common bus

摘要

A method and apparatus for selecting a particular node from a plurality of nodes connected to a common bus to allow the node to use the bus. The nodes have a pre-determined priority. After initially enabling the nodes, the bus is monitored for a bus idle condition. It is then determined which of the nodes are enabled message nodes, which are enabled nodes that have a message to send on the bus. There is then arbitration between the enabled message nodes after the bus is in the bus idle condition for a first period of time, such that the enabled message node having the highest pre-determined priority among the enabled message nodes is disabled for arbitration purposes, and also at the same time selects a target and performs a transfer. This procedure is repeated until all the enabled message nodes have been disabled. Thereafter, all of the nodes on the bus are enabled when the bus is in the bus idle condition for a second period of time, which is longer than the first period of time.