— Emulating Output Queued (OQ) Switch with sustainable implementation cost and low fixed delay is always preferable in designing high performance routers. The SwitchMemory-Switch (SMS) router, also called Distributed Shared Memory (DSM) Switch, provides a possible way towards practically emulating OQ in backbone switches. However, the architectures and algorithms for SMS switches ever proposed are either unpractical or only supporting First-Come-First-Serve (FCFS) scheduling policy, which cannot support QoS and is unfair for light traffic flow. Our improved SMS architecture and algorithm aim at emulating Push-In-First-Out (PIFO) OQ. We employ a randomly-dispatching first stage and resolve memory access conflictions on the second stage of the switch through a probabilistic matching method, at the cost of fixed delay and sufficiently low cell loss probability (PCLP). The relative fixed delay of our algorithms for an N×N switch is composed of two parts: N and (-3/2log2PCLP), which resu...