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Evolution of Microprocessors
Early integrated circuits
4-bit microprocessors
8-bit microprocessors
16-bit microprocessors
32-bit microprocessors
Recent microprocessors
Microcontrollers and digital signal processors
This chapter gives a crisp outline of the various stages in the evolution of today's microprocessors. Explicit information is given right from the integrated circuits through the 4-, 8-, 16- and 32-bit microprocessors to the present-day microprocessors and microcontrollers.
1.1 EARLY INTEGRATED CIRCUITS
The 1939–45 world war posed stringent envorinmental and operation requirements like standardization, miniaturization, reliability, maintainability and the like on electronic communication equipment components. Key improvements took place in the design and manufacture of electronic components. After the war, the semiconductor transistor came into widespread use.
The concept of integrated circuit (IC), also known as ‘chip’, which integrates a circuit of several electronic components into a solid block was envisaged in 1952. In 1959, the invention of planar process with aluminium metallization by Robert Noyce and Jean Hoerni at Fairchild Semiconductor enabled large-scale production of ICs.
The progress of integration of circuitry was very rapid. The small-scale integration (SSI) chip having digital logic gates circuitry was introduced in 1964. Gordon Earle Moore at Fairchild Semiconductor predicted that the number of transistors on a silicon chip would increase from 50 in 1965 to 65,000 in 1975. It was recognized as his first articulation of Moore's law suggesting that the number of transistors on a chip will double every year. Moore's prediction indeed was true and medium-scale integration (MSI) chip with a complete register circuit appeared in 1968. The large-scale integration (LSI) memory chip (256-bit RAM) was produced by Fairchild in 1970. In 1971, the LSI chips with 1024-bit dynamic random access memory (RAM) and Universal Asynchronous Receiver Transmitter (UART) were developed.
1.2 4-BIT MICROPROCESSORS
The advent of microprocessors was accidental. Intel Corporation founded by Moore and Noyce in 1968 was initially focused on creating semiconductor memory (DRAMs and EPROMs) for digital computers. In 1969, a Japanese calculator manufacturer – Busicom approached Intel with a design for a small calculator, which required 12 custom chips. Ted Hoff, an Intel engineer felt that a general-purpose logic device could replace the separate multiple components. This idea led to the development of the first microprocessor. Microprocessors made a modest beginning as the drivers for calculators.
Federico Faggin and Stanley Mazor realized Ted Hoff's ideas into hardware at Intel. The result was the Intel 4000 family comprising the 4001 (2K ROM), the 4002 (320-bit RAM), the 4003 (10-bit I/O shift-register) and the 4004, a 4-bit central processing unit (CPU). Intel introduced the 4004 microprocessor to the worldwide market on November 15, 1971. It was a 4-bit PMOS chip with 2,300 transistors. It was not truly a general-purpose microprocessor as it was basically designed for a calculator. About the same time, Texas Instruments also developed the 4-bit microprocessor TMS 1000. Texas Instruments is recognized as the inventor and owner of the microprocessor patent.
1.3 8-BIT MICROPROCESSORS
Federico Faggin and his team at Intel designed a chip for controlling a CRT display produced by Computer Terminals Corporation, later called Datapoint. This chip did not meet Datapoint's functional requirement of speed and they decided not to use it. Intel introduced this chip as world's first 8-bit general-purpose microprocessor 8008 in 1972. The Intel 8008 was used in the famous Mark-8 computer kit. On realizing the potential of this product, Intel introduced the improved 8008, the 8080 microprocessor in 1974. The Intel 8080 really created the microprocessor market. The other notable 8-bit microprocessors include Motorola 6800, designed for use in automotive and industrial applications, and Rockwell PPS-8, Signetics 2650 having innovative and powerful instruction set architecture.
With improvements in integration technology, Intel was able to integrate the additional chips required by the 8080, that is, the 8224 clock generator and the 8228 system controller along with the 8080 microprocessor within a single chip – the Intel 8085. The other improved 8-bit microprocessors include Motorola MC6809 designed for high performance, Zilog Z-80 and RCA COSMAC designed for aerospace applications.
In 1975, Moore recalled that his prediction of exponential growth in the complexity of integrated circuits was true. He also forecast a change for the next decade indicating that the pace of complexity increase would slow to a doubling every two years during the maturation of design capabilities.
With increase in processing power the microprocessors dominated as the CPU of digital computers. Earlier to the arrival of microprocessors, CPU was realized from individual SSI chips. The digital computer that uses a single chip microprocessor as its CPU is referred to as a microcomputer.
1.4 16-BIT MICROPROCESSORS
Intel introduced the 16-bit microprocessor 8086 (16-bit bus) in 1978 and 8088 (8-bit bus) in 1979. It had 29,000 transistors. IBM selected the Intel 8088 for their personal computer (IBM-PC) introduced in 1981. Intel released the 16-bit microprocessor 80286 (having 1,34,000 transistors) which was used as CPU for the advanced technology personal computers (PC-AT) in 1982. It was called Intel 286 and was the first Intel processor that could run all the software written for its predecessor Intel 8088. This backward software compatibility was important for its commercial success. It is important to note that this software compatibility remains a hallmark of Intel's family of microprocessors.
1.5 32-BIT MICROPROCESSORS
In 1985, Intel announced the 80386 a 32-bit microprocessor with 2,75,000 transistors. It supported multitasking. Introduced in 1989, Intel 486 microprocessor was the first to offer a built-in math co-processor. It had 1.2 million transistors.
In 1993, Intel Pentium microprocessor with 3.1 million transistors was introduced. It allowed computers to process real-world data like speech, sound, handwriting and photographic images. The 7.5-million transistor Intel Pentium II microprocessor, introduced in 1997, was designed specifically to process audio, video and graphics data efficiently. Intel Celeron processors range designed for the value PC market segment were released from 1999.
Intel Pentium III processors with 9.5 million transistors designed for advanced imaging, 3D, streaming audio, video and speech recognition applications and Intel Pentium III Xeon processors for workstation and server market segments were introduced in 1999. Intel Pentium IV processors with more than 42 million transistors introduced from 2000 are used in the present PCs. Users can create professional quality movies, deliver TV-like video via the internet, communicate with real-time video and voice, render 3D graphics in real time, quickly encode music for MP3 players and simultaneously run several multimedia applications while connected to the Internet.
Intel Xeon processors introduced from 2001 are targeted for high-performance and mid-range, dual-processor workstations, dual and multiprocessor server configurations coming in the range.
1.6 RECENT MICROPROCESSORS
The Itanium processor is the first in a family of 64-bit products from Intel introduced in 2001. It is well suited for the most demanding enterprise and high-performance computing applications like e-Commerce security transactions, large databases, mechanical computer-aided engineering and sophisticated scientific and engineering computing.
Introduced from 2003, the Intel Pentium M processor, the Intel 855 chipset family and the Intel PRO/Wireless 2100 network connection are the three components of Intel Centrino mobile technology. Intel Centrino mobile technology is designed specifically for portable computing, with built-in wireless local area network (LAN) capability and breakthrough mobile performance. It enables extended battery life and thinner, lighter, mobile computers.
1.7 MICROCONTROLLERS AND DIGITAL SIGNAL PROCESSORS
A microcontroller is a highly integrated chip that contains all the components comprising a controller. Typically, this includes a CPU, RAM, some form of read only memory (ROM), input/output (I/O) ports, timers and so on. Unlike a general-purpose computer, which also includes all of these components, a microcontroller is designed for a very specific task – to control a particular system. As a result, the number of parts can be reduced, which cuts down the cost. Microcontrollers are sometimes called embedded microcontrollers, which just means that they are part of an embedded system – that is, one part of a larger system. One of the popular 8-bit microcontrollers is Intel 8051.
Digital Signal Processor (DSP) is a special-purpose CPU used for digital signal processing applications. Once a signal is converted into digital data, its components can be isolated, analysed and rearranged more easily than in analogue form using various algorithms, such as Fast Fourier Transform. It provides ultrafast instruction sequences, such as shift and add, and multiply and add, which are commonly used in math-intensive signal processing. DSP is used in many fields, including biomedicine, sonar, radar, seismology, audio, cell phones, sound cards, fax machines, modems, hard disks, digital TV, speech and music processing, imaging and communications. It is also used to create the concert hall and surround sound effects in stereo and home theatre equipments. One of the popular DSP chips is TMS320C54X from Texas instruments.
Microprocessors, microcontrollers and DSP chips are used in business machines, automotive electronics, home appliances, electronic toys, variety of industrial applications and the like. Today, there is no field in which microprocessors, microcontrollers or DSP chips have not made an impact.
Semiconductor Industries Association (SIA) has projected annual sales in the year 2006 for microprocessors, microcontrollers and DSPs as $36.4 billion, $12.3 billion and $9 billion, respectively.