Multiple computers

The days of one large computer serving an entire organization are long gone. To- day, computers hide in unforeseen places like automobiles and cameras. In fact, your personal “computer” (in the singular) contains more than one processor: the graphics processor is a computer specialized for the task of taking information from the computer’s memory and rendering it on the display screen. I/O and commu- nications interfaces are also likely to have their own specialized processors. Thus, in addition to the multitasking performed by the operating systems kernel, parallel processing is being carried out by these specialized processors.

The use of multiple computers is also essential when the computational task re- quires more processing than is possible on one computer. Perhaps you have seen pictures of the “server farms” containing tens or hundreds of computers that are used by Internet companies to provide service to millions of customers. In fact, the entire Internet can be considered to be one distributed system working to dissemi- nate information in the form of email and web pages.

Somewhat less familiar than distributed systems are multiprocessors, which are systems designed to bring the computing power of several processors to work in concert on a single computationally-intensive problem. Multiprocessors are exten- sively used in scientific and engineering simulation, for example, in simulating the atmosphere for weather forecasting and studying climate.