Abstract: A multicomputer is shown made up of a crossbar network to which are connected processing nodes and I/O interface nodes. The processing nodes include crossbar interface circuits that provide routing signals in local registers so that a local processor can access memory in remote processing nodes. The crossbars include circuits to establish communication paths through the crossbar networks in response to the routing signals, so that a local processor has direct access to remote memory, which is mapped into local address space. The routing signal can have a broadcast mode and can establish priority for the signal. Under some circumstances the crossbar circuit can choose between alternative paths through a crossbar. Arbitrary sized and shaped networks of crossbars can be readily implemented, and the direct memory burst transactions allow very high speed performance.