Topsy: an extensible Unix multicomputer

Topsy is a message passing multicomputer architecture. It comprises a distributed Unix-compatible kernel resting on a message software system which in turn relies on a new, high speed, communications hardware. The authors present an overview of the goals of the architecture and the main design decisions, a description of the structure and major components of the operating system and the communications hardware, an evaluation, and discussion of future developments. Topsy is built on a distributed kernel and inexpensive communications hardware. This makes it feasible to build multicomputers which can be incrementally enhanced over a large range of sizes. The key features of the architecture are: fully distributed network based parallel kernel; distributed Unix file system maintaining full Unix semantics and integrating transparently with existing Unix tools; load balancing, to dynamically distribute work among processors; cheap and fast communications hardware; and easily extensible-from 1 to 256 processors at present but essentially without limit