Performance aspects of switched SCI systems

The Scalable Coherent Interface (SCI) defines a high-speed interconnect that provides a coherent distributed shared memory system. With the use of switches separate rings can be connected to form large topology-independent configurations. It has been realized that congestion in SCI systems generates additional retry traffic which reduces the available communication bandwidth. This paper investigates additional flow control mechanisms for overloaded switches. They are based on a supplementary retry delay and show a significant throughput gain. Furthermore two different management schemes for the output buffers are investigated. Computer simulations are used to compare the models and to determine system parameters.