SIMD Architecture

• The SIMD model of parallel computing consists of two parts as shown in Fig. 2.7a. :
  1. a front-end computer of the usual von Neumann style,
  2. a processor array.
• Each processor in the array has a small amount of local memory where the distributed data resides while it is being processed in parallel.
• The similarity between serial and data parallel programming is one of the strong points of data parallelism.
• Processors either do nothing or exactly the same operations at the same time.
• In SIMD architecture, parallelism is exploited by applying simultaneous operations across large sets of data.
• There are two main configurations that have been used in SIMD machines (see Fig. 2.5).

Figure 2.8: Two SIMD Schemes.

1. Each processor has its own local memory.
   • Processors can communicate with each other through the interconnection network.
   • If the interconnection network does not provide direct connection between a given pair of processors, then this pair can exchange data via an intermediate processor.
2. In the second SIMD scheme,
   • Processors and memory modules communicate with each other via the interconnection network.
   • Two processors can transfer data between each other via intermediate memory module(s) or possibly via intermediate processor(s).