Distributed Memory
In distributed memory MIMD machines, each processor has its own individual memory location. Each processor has no direct knowledge about other processor's memory. For data to be shared, it must be passed from one processor to another as a message. Since there is no shared memory, contention is not as great a problem with these machines. It is not economically feasible to connect a large number of processors directly to each other. A way to avoid this multitude of direct connections is to connect each processor to just a few others. This type of design can be inefficient because of the added time required to pass a message from one processor to another along the message path. The amount of time required for processors to perform simple message routing can be substantial. Systems were designed to reduce this time loss and hypercube and mesh are among two of the popular interconnection schemes.
As examples of distributed memory(multicomputers): MPP (massively parallel processors) and COW (Clusters of Workstations). The first one is complex and expensive: lots of super-computers coupled by broad-band networks. Examples: hypercube and mesh interconections. COW is the "home-made" version for a fraction of the price.
Read more about this topic: MIMD
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