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Machines like the SGI Origin 2000 have a distributed shared memory with a so called directory implementation (pioneered in DASH project at Stanford) of cache coherence
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Machines like SGI Cray T3E are distributed memory but do have fast get and put so as to be able to access single variables stored on remote memories
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This gives performance advantage of shared memory without the programming advantage but complex hardware of Origin 2000
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Origin 2000 approach does not scale as well as Cray T3E and large Origin 2000 systems must use message passing to link 128 node coherent memory subsystems
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Cray T3E offers a uniform (but not as good for small number of nodes) interface
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Message passing / distributed memory is natural web model
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