Multicomputersbuiltaround a general network are now a viable alternative to multicomputersbased on a system-speci~c interconnect because of architectural improvements in two areas.First, the host-network interface overhead can be minimized by reducing copy operations and host interrupts.Second, the network can provide high bandwidth and low latency by using high-speed crossbar switches and efficient protocol implementations.While still enjoying thejexibility of general networks, the resulting network-based multicomputers achieve high performance for typical multicomputer applications that use system-specijic interconnects.We have developed a network-based mtdticomputer called Nectar that supports these claims.