| Summary: | Object-based distributed shared memory systems allow processes on different machines to communicate through passive shared objects. This paper describes the implementation of such a system on a transputer grid. The system automatically takes care of placement and replication of objects. The main difficulty in implementing shared objects is updating replicated objects in a consistent way. We use totally-ordered group communication (broadcasting) for this purpose. We give four different algorithms for ordering broadcasts on a grid and study their performance. We also describe a portable runtime system for shared objects. Measurements for three parallel applications running on 128 T800 transputers show that good performance can be obtained. Keywords: Distributed Shared Memory, shared objects, Orca, parallel programming languages, transputers, Parix, totally-ordered group communication, broadcasting. 1 Introduction Distributed shared memory (DSM) is an attractive alternative to message p.
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