THE SP2 HIGH-PERFORMANCE SWITCH

The heart of an IBM Sp2(TM) system is the High-Performance Switch, whi ch is a low-latency, high-bandwidth switching network that binds toget her RISC System/6000(R) processors. The switch incorporates a unique c ombination of topology and architectural features to scale aggregate b andwidth, enhance reliability, and simplify cabling. It is a bidirecti onal multistage interconnect subsystem driven by a common oscillator a nd delivers both data and service packets over the same links. Switchi ng elements contain a dynamically allocated shared buffer for storing blocked packet flits. The switch is constructed primarily from switchi ng elements (the Vulcan switch chip) and adapters (the SP2 communicati on adapter). The SP2 communication adapter uses a variety of technique s to improve bandwidth and offload communication tasks from the node p rocessor. This paper examines the switch architecture and presents an overview of its support software.