Transputer Networks

Simple Transputer Connections

Typical transputer hardware provides four bidirectional communications links. These links may be used to connect transputers in any arbitrary geometry, subject to the limit of connections and the program's execution pattern. Transputers are not network nodes with routing capabilities, so all communications must occur in a point to point fashion or with explicit forwarding. The specific topology for a transputer network must be configured by the software developer, with occam processes mapped to transputers appropriately.

Transputers are immediately useful for pipelines containing a linear data flow, systolic arrays containing a 2D mesh of operations, and ring orientations:

Image - Ring

The systolic and linear pipeline orientations made transputer networks particularly attractive for high speed image, sound, and video processing operations.

More Advanced Connections

The most interesting, and perhaps most useful, aspect of the transputer interconnection system is its flexibility and potential for easily building large multidimensional transputer networks. Although each transputer only contains four communications links, two transputers may be connected to create a "node" with six bidirectional links (Brookes, 1989):

Image - Two Transputer node

Because each node has six interconnects, it may be used to create arbitrary three dimensional lattice structures, such as the following hypercube:

Image - Hypercube

This lattice can be extended in all directions! The transputer interconnect may be configured to support 3D mesh and 3D torus connection topologies, from which most other specific networks may be derived. Even today, only a few supercomputer systems, such as the Cray T3E, support a hardware 3D torus interconnect.

Before multiple processes may be run on multiple transputers, however, it's necessary to describe the structure of a single process in occam. The next section introduces primary processes and the language elements necessary to construct useful occam programs.

Next: Processes
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