Abstract: High performance interconnection network switch plays a critical role in high performance computing (HPC) systems. As upper layer applications of the HPC, scientific computations demand not only low latency and high bandwidth of switch, but also hardware support of collective communications, such as broadcast, multicast, and barrier, etc. HyperLink switch, the core component of Dawning 5000 interconnection networks, has 38.4ns single stage latency and 160Gbps aggregated bandwidth, furthermore it supports 16 multicast groups and 16 barrier groups simultaneously. In the ideal condition, 1024 nodes can finish multicast and barrier operations within 2μs, which greatly improves the performance of scientific application. A cycle-accurate switch model is also built to evaluate switch performances. The simulation proves that 3 virtual channels are the best performance-cost choice for 16-port input-buffered switch, and that 4KB input buffer is sufficient for 1KB MTU switch to achieve the highest unicast throughput. A comparison between multi-rail networks and single-rail networks which have the same bandwidth as multi-rail networks is also given in theoretical analyses. It is shown that the former could effectively minimize the network latency, and thus provides much higher network throughput than the latter. The LogP model is employed to evaluate HyperLink multicast and barrier performances, which shows that the HyperLink switch has good scalability, easily supporting up to thousands of nodes.