MIMD System Architecture

Each of the individual nodes discussed in the previous section can be a MIMD parallel computer. Larger MIMD machines can be constructed by connecting many MIMD nodes via a high-performance network. While each node can have shared memory, memory is typically not shared between the nodes, at least not at the hardware level. Such machines are referred to as distributed memory computers or clusters, and in this section we consider such parallel computers in more detail. 

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MIMD systems aUow several processes to share a common set of processors and resources, as shown in Fig. 19.6(b). Multiple processors are joined together in a cooperating environment to execute programs. TypicaUy, one process executes on each processor at a time. The difficulties with traditional MIMD architectures He in fuUy utiUzing the resources when instruction streams staU (due to data dependencies, control dependencies, synchronization problems, memory accesses, or I/O accesses) or in assigning new processes quickly once the current process has finished execution. An important problem with this structure is that... 

There are many types of possible computer architecture, including parallel architectures [1, 2]. However, by far the most common one for simulators is the so-called MIMD architecture (multiple instruction stream - multiple data stream). On MIMD machines, each processing element is able to act independently (unlike some other specialist parallel machines). This provides maximum flexibility to the programmer, and unsurprisingly MIMD machines make up most of todays parallel systems. 

FinaUy, for molecular dynamics production runs on complex systems, it seems already clear now that the most cost-effective machines will be dedicated computers with MIMD architecture, but built up from special purpose processors... 

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