Parallel computing is the simultaneous execution of the same task (split up and specially adapted) on multiple processors in order to obtain results faster. The idea is based on the fact that the process of solving a problem usually can be divided into smaller tasks, which may be carried out simultaneously with some coordination.
A parallel computing system is a computer with more than one processor for parallel processing. In the past, each processor of a multiprocessing system always came in its own processor packaging, but recently-introduced multicore processors contain multiple logical processors in a single package.
There are many different kinds of parallel computers. They are distinguished by the kind of interconnection between processors (known as "processing elements" or PEs) and memory.
Pipelining is a method of increasing system performance and throughput. It takes advantage of the inherent parallelism in instructions. Instructions are divided into 5 stages : IF, ID, EX, MEM, WB. In pipelining, we try to execute 2 or more instructions at the same time thereby increasing the throughput. For more info on pipelining refer to the following website:
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With regards to Silicon area and speed, Pipelining takes up more Silicon area. This is because in hardware pipelining we duplicate the few units. In terms of speed, pipelining increases system performance and speed.