多处理与单处理

w3cstandard

A uniprocessor（UP）can accomplish parallelism inside the processor itself．For example，the fixed point unit and the floating point unit can run several instructions within the same CPU（central processing unit）cycle．Power，Power2 and Power PC architectures have a very high level of instruction parallelism．However，only one task at a time can be processed．

Uniprocessor designs have built-in bottlenecks．The address and data buses restrict data transfers to a one -at-a-time flow of traffic．[1] The program counter forces instructions to be run in strict sequence．Even if improvements in performance are achieved by means of faster processors and more instruction parallelism，operations are still run in strict sequence．However，in a uniprocessor，an increase in processor speed is not the total answer because other factors，such as the system bus and memory，come into play．[2]

Adding more processors seems to be a good solution to increase the overall performance of a system．Having more processors in the system increases the system throughput because the system can perform more than one task at a time．However，the increase in performance is not directly proportional to an increase in the number of processors because there are many other factors to be taken into consideration，such as resource sharing．

多处理与单处理

单处理器（UP）能在该处理器内部实现并行性，例如，在同一CPU周期内，定点部件和浮点部件可以运行几条指令。Power、Power2和Power PC体系结构具有非常高的指令级并行性，然而，一次只能处理一个任务。

单处理器的设计有内在的瓶颈，地址和数据总线限制了数据传送一次仅有一个的业务流。程序计数器迫使指令按严格的顺序运行。即使采用更快的处理器和更多的指令并行性使性能得以改善，但是操作始终按严格的顺序进行。而且，在单处理机中，提高处理器速度不能解决全部问题，因为其他因素，如系统总线和存储器也在起作用。

看来增加更多的处理器是提高系统整体性能的良好解决方案。系统中有多个处理器，由于同一时刻能完成不止一个任务而提高了系统的吞吐量。然而性能的提高与处理器的增加并非简单的正比关系，因为还有很多其他因素要考虑，例如资源共享。

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