Because of its programmability a stored program

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Unformatted text preview: ch means that it can undertake any task that can be described by a suitable algorithm. Sometimes this is reflected by its configuration as a desktop machine where the user runs different programs at different times, but sometimes it is reflected by the same processor being used in a range of different applications, each with a fixed program. Such applications are characteristically embedded into products such as mobile telephones, automotive engine-management systems, and so on. Computer applications 1.2 Abstraction in hardware design Computers are very complex pieces of equipment that operate at very high speeds. A modern microprocessor may be built from several million transistors each of which can switch a hundred million times a second. Watch a document scroll up the screen 4 An Introduction to Processor Design on a desktop PC or workstation and try to imagine how a hundred million million transistor switching actions are used in each second of that movement. Now consider that every one of those switching actions is, in some sense, the consequence of a deliberate design decision. None of them is random or uncontrolled; indeed, a single error amongst those transitions is likely to cause the machine to collapse into a useless state. How can such complex systems be designed to operate so reliably? Transistors A clue to the answer may be found in the question itself. We have described the operation of the computer in terms of transistors, but what is a transistor? It is a curious structure composed from carefully chosen chemical substances with complex electrical properties that can only be understood by reference to the theory of quantum mechanics, where strange subatomic particles sometimes behave like waves and can only be described in terms of probabilities. Yet the gross behaviour of a transistor can be described, without reference to quantum mechanics, as a set of equations that relate the voltages on its terminals to the current that flows though it. These equations abstract the essential behaviour of the device from its underlying physi...
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This document was uploaded on 10/30/2011 for the course CSE 378 380 at SUNY Buffalo.

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