Click for next page ( 15

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 14
:mpwessor : ...... . .. ~ ....~. ~. ~ .. ~. ~.~. ~ .mtcroprocessor- a tiny ....................... . ~nputer on a chip no .............. tiger than your fingernail room. At work, they help design complex buildings and control huge manufacturing has quickly and quietly machines. In between, they infiltrated our lives since it coordinate traffic lights and was introduced in 1971. At improve fuel efficiency in cars. home, microprocessors are the And everywhere there is a A web of electronic circuitry spreads across the face of the 4004, the first microprocessor. The chip contains 2,300 transistors yet measures only '/s inch by '/~ inch, about the size of a child's fingernail. 4 personal computer, there is a e microprocessor c turning ~ away 1nslc e. brains in electronic devices that control microwave ovens and change television channels from across the A microprocessor works something like a juke box's record player, which plays the tune on a record retrieved from its collection. A microprocessor, however, plays the set of instructions retrieved from a memory chip, performing simple functions such as addition or subtraction programmed into the instructions. Microprocessor and memo- ry chips alike rely on microscopic integrated circuits to perform their tasks. Before microprocessors, integrated circuit chips were generally not programmable. They could do only a single function for which they were designed, like a record player playing one tune engraved on its turntable. The first microprocessor, in fact, was developed by an American engineer who was given the task of designing 12 single-function chips for a Japanese calcula- tor. Instead, the engineer designed one general-purpose chip that performed all 12 functions according to instructions stored in a memory chip. Because each instruction c ontained only four bits-the electronic l's E N G I N E E R I N G A N D T H E A D V A N C E M E N T O F H U M A N W E L F A R E

OCR for page 14
and O's of digital code the microprocessor was classified a 4-bit chip. Microprocessors of the first generation were too feeble to power anything resem- bling a personal computer. But they were and still are powerful enough to drive pocket calculators and control machines performing simple tasks. They have become, like the motor, a tool for every use. Millions are sold each year to operate home burglar alarms, remote television controllers, programmers for videocassette recorders, and dozens of toys. The "~bitter" was the hottest selling microprocessor every year until 1988, when 8-bit chips took the lead. Microprocessor chips in a variety of sizes provide the delicate control that improves the efficiency of power plants, cars, and heating and cooling systems in buildings, which translates into lower operating costs and less pollution. They are also widely used in the cockpits of advanced commercial airliners to control navigation and other avionics systems, thereby improving the efficiency of aircraft and crew. Second-generation microprocessors- the mighty 8-bit chips that appeared in 1974 had enough calculating power to operate low-performance computers. These "microcomputers" were built around microprocessors and remained curiosities, the electronic playthings of hobbyists, until MICROPROCESSOR Microprocessors are the tiny "brains" inside microcomputers and hundreds of other electronic devices. 15

OCR for page 14
Microprocessors make modern airliners easier to fly by displaying flight instrument data on video screens, as in the cockpit of this advanced 747. These data display screens and other design improvements helped reduce the number of cockpit lights, switches, and gauges to fewer than 400 in this aircraft compared with nearly 1,000 in earlier models. ~ ,~.1 ............... : i,,,l --- 1-1 Small, inexpensive personal computers built around microprocessors bring computer power into millions of homes around the world. Ready-to-use programs have made it easy for children as well as adults to use these computers for video games, word processing, and dozens of other applications. 6 the introduction of third-generation chips in 1975. These delivered much better perfor- mance than their forerunners and brought down microprocessor prices to as low as $25 from nearly $200. Within two years, they spawned commercial lines of home micro- computers that were soon being used for nonhome tasks. It was, however, the fourth generation- mostly the powerful 16-bit microprocessors- that convinced the traditional computer industry that microcomputers based on these chips were powerful enough for more than home video games. And in 1981 the main- frame-computer industry began marketing microcomputers for such computational tasks as graphics, desktop publishing, managing large data bases, and computer- aided design in business and industry. Microcomputers would have been useless without software, the programs of simple commands that tell computers how to perform complex tasks. Each computer has coded operating instructions already wired into it, but they are awkward for people to use. So the codes have been translated into languages, such as BASIC, FORTRAN, and COBOL, based on easy-to-use words and symbols. The languages further simplify programming by using single symbols for some simple functions that are generated by a series of instructions. For example, "a" might trigger the series of instructions for the function "multiply". The languages, in turn, are used to program larger sets of instruc- tions, or programs, that perform complex tasks such as word processing. For instance, word processing software might be pro- grammed so that typing C-O-P-Y initiates the thousands of instructions for duplicating a page of text on the computer screen. Software was not readily available for the earliest microcomputers. Hobbyists labored to compose their own operating systems programs telling a computer how to run itself and application programs for tasks such as word processing or playing Space Invaders. However, a cottage industry of programmers began to sprout in the mid- 1970s and was soon turning out commercial programs for a multitude of applications, including word processing, video games, inventory control, and personal finance management. The combination of ready-made soft- ware and low-cost microcomputers pro- duced the true personal computer, a machine so affordable and easy to use that it was available to almost everyone. The impact has been enormous. PCs have done for comput- ing power what the printing press did for knowledge gave it to the masses. Connect- ed by telephone lines, PC users tap into networks of computers as well as into data banks for stock quotations, medical informa- tion, and legal cases. In the future they may be able to draw on data bases of library books, newspapers, and magazines from all over the world. I E N G ~ N E E R ~ N G A N ~ T H E ~ D VA N C E M E N T O F H U M A N W E ~ FA R E

OCR for page 14
Today's microprocessors greatly outper- form their 4-bit ancestors. One 32-bit chip, for example, is a thousand times faster. Another carries 500 times more transistors, packing 1 million of them onto a chip no bigger than a postage stamp. Others made by a process called CMOS, for complementary metal- oxide semiconductor use less energy and produce less heat than conventional chips. They are used in satellites, portable comput- ers, and other devices where energy con- sumption is critical. The speed of some microprocessor chips has been improved by a design known as RISC, or reduced instruc- tion set computer, which uses a small number of simple instructions. Complex instructions, which occur infrequently, are handled in software. Larger memory chips have also been developed to hold the complex programs that exploit the power of the new microprocessors. In the future, multipurpose microproces- sor chips will probably grow to 64 bits, some containing as many as 10 million transistors. Application-specific processors will be designed for just a few specific tasks. Such chips are faster and more efficient at a single job than a chip designed to do everything. The key to making application-specific processors will be advanced computer-aided design (CAD) systems themselves based on microprocessor chips that design such specialized chips quickly and inexpensively. The new microprocessors and the systems they run will have the power to generate better graphics and higher-quality three-dimensional images for CAD systems. Microcomputers, for example, will certainly be more adept at human talents, such as understanding spoken words, speaking, or even learning and reasoning artificial intelligence. And they will be able to process incredible amounts of data at lightning speeds. Work is under way on a new genera- tion of supercomputers, which would link hundreds, even thousands, of m~croproces- sors in parallel arrays. Each chip would work on a different part of a massive problem, such as a global weather forecast, solving the entire problem in a fraction of the time needed if each part were solved one after the other. The challenge of parallel-array systems is to develop mathematical formulas and operat- ing systems to coordinate the work of all the microprocessors. An even greater challenge lies in figur- ing out how to take best advantage of the wonderfully powerful computers based on these new microprocessors. That is the task of the programmers, whose work is limited only by their ability to think creatively. The i486 microprocessor squeezes 1.18 million transistors-500 times mare than the 'I. MICROPROCESSOR I microprocessor-onto a chip about the size of an adult's thumbnail. 17