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The Development Of CPUs

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Introduction

CPUs The History And Development A central processing unit (CPU), or sometimes simply processor, is the component in a digital computer that interprets computer program instructions and processes data. CPUs provide the fundamental digital computer trait of programmability, and are one of the necessary components found in computers of any era, along with primary storage and input/output facilities. A CPU that is manufactured, as a single integrated circuit is usually known as a microprocessor. Beginning in the mid-1970s, microprocessors of ever-increasing complexity and power gradually supplanted other designs, and today the term "CPU" is usually applied to some type of microprocessor. The phrase "central processing unit" is a description of a certain class of logic machines that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term "CPU" ever came into widespread usage. However, the term itself and its initialize have been in use in the computer industry at least since the early 1960s (Weik 1961). ...read more.

Middle

Since the term "CPU" is generally defined as a software (computer program) execution device, the earliest devices that could rightly be called CPUs came with the advent of the stored-program computer. The idea of a stored-program computer was already present during Erica's design, but was initially omitted so the machine could be finished sooner. On June 30, 1945, before ENACT was even completed, mathematician John von Neumann distributed the paper entitled "First Draft of a Report on the EVA." It outlined the design of a stored-program computer that would eventually be completed in August 1949 EVA was designed to perform a certain number of instructions (or operations) of various types. These instructions could be combined to create useful programs for the EVA to run. Significantly, the programs written for EVA were stored in high-speed computer memory rather than specified by the physical wiring of the computer. This overcame a severe limitation of ENACT, which was the large amount of time and effort it took to reconfigure the computer to perform a new task. ...read more.

Conclusion

For example, building direct current sequential logic circuits out of relays requires additional hardware to cope with the problem of contact bounce. While vacuum tubes do not suffer from contact bounce, they must heat up before becoming operational and eventually stop functioning altogether. Usually, when a tube failed, the CPU would have to be diagnosed to locate the failing component so it could be replaced. Therefore, early electronic (vacuum tube based) computers were generally faster but less reliable than electromechanical (relay based) computers. Tube computers like those that EDNA tended to average eight hours between failures, whereas relay computers like the (slower, but earlier) Harvard Mark I failed very rarely (Weik 1961:238). In the end, tube based CPUs became dominates because the significant speed advantages afforded generally outweighed the reliability problems. Most of these early synchronous CPUs ran at low clock rates compared to modern microelectronic designs (see below for a discussion of clock rate). Clock signal frequencies ranging from 100 kHz to four MHz were very common at this time, limited largely by the speed of the switching devices they were built with. ?? ?? ?? ?? Tim Nash11LY ...read more.

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