|The SB-PRAM is a MIMD parallel computer with shared address space and uniform memory access time (CRCW-PRAM-Model). Processors and memory modules are connected by a butterfly network. Each SB-PRAM processor module consists of a custom ASIC processor with extended Berkeley-RISC instruction set, a local program memory and SCSI interface. Network nodes and memory modules provide hardware support for concurrent read and concurrent write memory access and parallel prefix operations. Network latency is hidden by pipelining several virtual processors (hardware threads with zero switching overhead) on one physical processor. Network congestion is reduced by hashed addresses. Hot spots are avoided by combining.