During the period following the completion of the Cosmic Cube experiment [1], and while commercial descendants of this first-generation multicomputer (message-passing concurrent computer) were spreading through a community that includes many of the attendees of this conference, members of our research group were developing a set of ideas about the physical design and programming for the second generation of medium-grain multicomputers. Our principal goal was to improve by as much as two orders of magnitude the relationship between message-passing and computing performance, and also to make the topology of the message-passing network practically invisible. Decreasing the communication latency relative to instruction execution times exten...