Latest revision as of 22:43, 6 September 2024

A microprocessor (µP) or a Microprocessing Unit (MPU) is a device that implements the core elements of a computer system on a single integrated circuit, or as a few integrated circuits operating as a cohesive unit, designed for the processing digital data.

Modern microprocessors typically incorporate the functionality of a clock, central processing unit (CPU), arithmetic logic unit (ALU), floating point unit (FPU), control unit (CU), memory management unit (MMU), interrupts, input/output interfaces, and cache. Specialized microprocessor may also serve as graphical processing units (GPUs), signal processing units (DSPs), neural processing unit (NPUs), microcontrollers, etc.

Overview[edit]

Microprocessors are instruction set processors (ISPs), meaning they operate on a predefined set of instructions. In the broadest sense, their basic functionality is to continuously read in digital data consisting of instructions and possibly values; execute them by interpreting the instructions and performing a certain operation on the values; and finally outputs a result.

While the basic functionality is shared among all microprocessors, they vary greatly in the type and size of data they handle, the kind of operations they support, how they perform those operations, their intended purpose, and their performance characteristics. The functionality of a microprocessor is dependent on the characteristics of the instruction set it operates on. Every program that runs on that microprocessor is therefore bound by that instruction set architecture (ISA) and is encoded in that instruction set. The instruction set architecture is the specification of a microprocessor design while the realization of an ISA is known as the implementation. There can, and usually are, multiple implementations for a second ISA specification. Those implementations are known as microarchitectures. The kind of tradeoffs made in a microarchitecture ultimately determines the characteristics of the microprocessor (e.g., power and performance).

Variants[edit]

Microprocessors come in various flavors. Most microprocessors can be classified as follows:

• general-purpose microprocessors - the most common form of microprocessors, not designed for any one specific task in mind. Instead they are designed to support a broad array of operations.
• bit-slice microprocessor (BSM) - a microprocessor designed as a module intended to be built up like Lego blocks into a desired word size and architecture as needed.
• system on chip (SoC) - a microprocessor that contains all the components of a computer system, including the extra functionality that would normally be provided by auxiliary chips, which could include things such as wireless, ethernet, SD card, ADC, DAC, LCD drivers, and FPGA. SoCs are capable of running full-fledged modern operating systems with all their features.
• microcontroller (MCU) - a microprocessor that contains a few additional components such as RAM, ROM, and programmable I/O ports primarily designed to control and drive other electronic equipment. MCUs are designed to be embedded, usually in a highly restrictive environment. They usually consume very little power, may run relatively slow, and typically execute individual task-specific programs.
• digital signal processor (DSP) - a microprocessor that specializes in the numerical manipulation of signals.
• floating point unit (FPU) - is a math microprocessor (or coprocessor) - a microprocessor that specializes in the creation and manipulation of floating point values.
• graphics processing unit (GPU) - is a graphics microprocessor - a microprocessor that specializes in the creation and manipulation of images through a set of optimized geometric operations. Modern graphic microprocessors tend to be highly parallelized, allowing large blocks of visual data to be processed efficiently.
• vector processor (VPU) - a vector processor is microprocessor that implements operations that manipulate one/multi-dimensional arrays of data known as vectors.
• physics processing unit (PPU) - a microprocessor that specializes in handling the calculations of physics. This includes things such as fluid dynamics and collision detection.
• neural processing unit (NPU) - is a neural microprocessor - a microprocessor that specializes in the manipulations of predictive models.
• coprocessor - a microprocessor that aides a master microprocessor by either offloading some of its work or by providing additional specialized processing operations, e.g. cryptography, math, graphics, string processing, or I/O interfacing. A coprocessor can act as an extension of the master microprocessor by extending the instruction set architecture or by acting like another peripheral on the main bus.

Some microprocessors can be a hybrid combinations of a few of the above. For example, a general-purpose microprocessor might come with an integrated GPU, implying an additional graphic processing unit has been added to the microprocessor to enable it to manipulate visual data more efficiently. Likewise almost all modern desktop microprocessors come with integrated floating point units.

Specifications[edit]

Main articles: central processing unit, architecture, microarchitecture, and instruction set architecture

The technical specifications of microprocessors are derived from the microarchitecture of the incorporated CPU, the semiconductor technology involved, and the properties of the overall system. Some common specifications are summarized below:

• instruction set architecture
• technology - the semiconductor technology used to create the MPU (e.g. CMOS, BiCMOS, and TTL)
• process - the process used to manufacture the MPU - i.e the feature size and design rules. The feature size on its own (e.g. 10 µm) is usually taken as a synonym for the process.
• microarchitecture - the functional description of the underlying circuitry of the microprocessor.
• word size - the word size of a microprocessor usually refers specifically to the data word size used - i.e. highest operand width used to manipulate standard integer values. (this excludes special processing units such as SIMD and FPU)
• core count - the number of physical cores incorporated into the chip.
• endianness - the order of the bytes the microprocessor uses when operating on multi-byte values.
• clock frequency - the internal operating frequency of CPU's core. It's one of many parameters that are used to assess the performance of a microprocessor.
• package - the physical casing of the microprocessor. This most often goes along with a socket, which is the interconnects that sits on the circuit board itself where the package is inserted into.

Note that not all the specifications listed above apply to all the types of microprocessors.

History[edit]

Main article: history of the microprocessor

The microprocessor has origins in the development of the MOSFET (metal-oxide-semiconductor field-effect transistor, or MOS transistor),^[1] which was first demonstrated by Mohamed M. Atalla and Dawon Kahng of Bell Labs in 1960.^[2] Following the development of MOS integrated circuit chips in the early 1960s, MOS chips reached higher transistor density and lower manufacturing costs than bipolar integrated circuits by 1964. MOS chips further increased in complexity at a rate predicted by Moore's law, leading to [large-scale integration]] (LSI) with hundreds of transistors on a single MOS chip by the late 1960s. The application of MOS LSI chips to computing was the basis for the first microprocessors, as engineers began recognizing that a complete computer processor could be contained on several MOS LSI chips.^[1] Designers in the late 1960s were striving to integrate the central processing unit (CPU) functions of a computer onto a handful of MOS LSI chips, called microprocessor unit (MPU) chipsets.

The advent of low-cost computers on integrated circuits has transformed modern society. General-purpose microprocessors in personal computers are used for computation, text editing, multimedia display, and communication over the Internet. Many more microprocessors are part of embedded systems, providing digital control over myriad objects from appliances to automobiles to cellular phones and industrial process control.

During the 1960s, computer processors were constructed out of small and medium-scale ICs—each containing from tens of transistors to a few hundred. These were placed and soldered onto printed circuit boards, and often multiple boards were interconnected in a chassis. The large number of discrete logic gates used more electrical power—and therefore produced more heat—than a more integrated design with fewer ICs. The distance that signals had to travel between ICs on the boards limited a computer's operating speed.

In the late-1960s, designers were striving to integrate the central processing unit (CPU) functions of a computer onto a handful of MOS LSI chips, called microprocessor unit (MPU) chip sets. Building on earlier Busicom designs and concepts from 1968, Intel introduced the first commercial microprocessor, the 4-bit Intel 4004, in 1971, followed by its 8-bit microprocessor 8008 in 1972.

The first microprocessors emerged in the early 1970s, and were used for electronic calculators, using binary-coded decimal (BCD) arithmetic on 4-bit words. Other embedded uses of 4-bit and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc., followed soon after. Affordable 8-bit microprocessors with 16-bit addressing also led to the first general-purpose microcomputers in the 1970s.

Since the early 1970s, the increase in capacity of microprocessors has followed Moore's law; this originally suggested that the number of components that can be fitted onto a chip doubles every year. With present technology, it is actually every two years,^[3] and as such Moore later changed the period to two years.^[4]

4-bit[edit]

Intel 4004 (1968-1971)[edit]

Main article: Intel 4004

Intel 4004 (1971), the first commercial microprocessor.

The Intel 4004 is generally regarded as the first commercially available microprocessor.^[5][6] The "Busicom Project"^[7] that produced the 4004 originated in 1968, when Busicom engineer Masatoshi Shima designed a special-purpose LSI chipset, along with his supervisor Tadashi Tanba, for use in the Busicom 141-PF high-performance desktop calculator.^[8] Busicom's original design called for a programmable chip set consisting of seven different chips. Three of the chips were to make a special-purpose CPU with its program stored in ROM and its data stored in shift register read-write memory.^[7] Shima's initial design included arithmetic units (adders), multiplier units, registers, read-only memory, and a macro-instruction set to control a decimal computer system.^[8] Sharp engineer Tadashi Sasaki was also involved with its development, and conceived of a single-chip CPU in 1968, when he discussed the concept at a brainstorming meeting that was held in Japan. Sasaki attributes the basic invention to break the calculator chipset into four parts with ROM (4001), RAM (4002), shift registers (4003) and CPU (4004) to an unnamed woman, a software engineering researcher from Nara Women's College, who was present at the meeting. Sasaki then had his first meeting with Intel in 1968, and discussed the woman's four-division chipset concept with Busicom and Intel.^[9]

The initial Busicom design, which consisted of seven chips, including a three-chip CPU, was eventually simplified down to four chips, including a single-chip CPU.^[7] This simplified approach was initially conceived by Sasaki, influenced by the unnamed Nara Women's College reseacher in 1968,^[9] and then designed by Intel's Ted Hoff in 1969.^[7] Hoff, the Intel engineer assigned to evaluate the project, believed the Busicom design could be simplified by using dynamic RAM storage for data, rather than shift register memory, and a more traditional general-purpose CPU architecture. Hoff's design consisted of a four-chip architectural proposal: a ROM chip for storing the programs, a dynamic RAM chip for storing data, a simple I/O device and a 4-bit central processing unit (CPU). Although not a chip designer, he felt the CPU could be integrated into a single chip, but as he lacked the technical know-how the idea remained just a wish for the time being.

The architecture and specifications of the MCS-4 came from the interaction of an Intel team led by Hoff and Stanley Mazor, a software engineer reporting to him, and a Busicom team led by Shima, in 1969.^[7] However, Mazor and Hoff moved on to other projects. In April 1970, Intel hired Italian-born engineer Federico Faggin as project leader, a move that ultimately made the single-chip CPU final design a reality. Shima meanwhile designed the Busicom calculator firmware and assisted Faggin during the first six months of the implementation. Faggin, who originally developed the silicon gate technology (SGT) in 1968 at Fairchild Semiconductor^[10] and designed the world’s first commercial integrated circuit using SGT, the Fairchild 3708, had the correct background to lead the project into what would become the first commercial general purpose microprocessor. Since SGT was his very own invention, Faggin also used it to create his new methodology for random logic design that made it possible to implement a single-chip CPU with the proper speed, power dissipation and cost. The manager of Intel's MOS Design Department was Leslie L. Vadász at the time of the MCS-4 development but Vadász's attention was completely focused on the mainstream business of semiconductor memories so he left the leadership and the management of the MCS-4 project to Faggin, who was ultimately responsible for leading the 4004 project to its realization. Production units of the 4004 were first delivered to Busicom in March 1971 and shipped to other customers in late 1971.^[11] The first known advertisement for the 4004 is dated November 15, 1971 and appeared in Electronic News.^[12]

NEC (1970-1973)[edit]

NEC released the μPD707 and μPD708, a two-chip 4-bit CPU, began development in 1970 and was released in 1971.^[13] They were followed by NEC's first single-chip microprocessor, the μPD700, in April 1972.^[14][15] It was a prototype for the μCOM-4 (μPD751), released in April 1973,^[14] combining the μPD707 and μPD708 into a single microprocessor.^[13]

8-bit[edit]

Microsystems International MF8008 (Intel 8008)

The Intel 4004 was followed in 1972 by the Intel 8008, the world's first 8-bit microprocessor. The 8008 was the precursor to the successful Intel 8080 (1974), which offered improved performance over the 8008 and required fewer support chips. It was designed by Masatoshi Shima and Federico Faggin.

12-bit[edit]

In 1973, Toshiba developed the TLCS-12,^[16][17] the world's first 12-bit microprocessor.^[18] The project began in 1971, when Toshiba began developing a microprocessor for Ford Motor Company's Electronic Engine Control (EEC) project, which went on to utilize Toshiba's 12-bit microprocessor.^[18]

16-bit[edit]

Panafacom MN1610 (1975), the first single-chip 16-bit microprocessor.

In 1975, Panafacom (a conglomeration of Fujitsu, Fuji Electric, and Matsushita) developed the first commercial 16-bit single-chip microprocessor CPU,^[19] the MN1610.^[20][21] According to Fujitsu, it was "the world's first 16-bit microcomputer on a single chip".^[19]

Components[edit]

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Design[edit]

A prototype of a RISC-V microprocessor with the heat spreader removed, showing the exposed die, January 2013

Main articles: integrated circuit and integrated circuit design

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Computational power[edit]

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Families[edit]

Main article: microprocessor family

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See also[edit]

• List of processor families
• History of computing hardware (1960s–present)
• Microprocessor chronology

References[edit]

Bibliography[edit]

• Advanced Microprocessors and Peripherals. India: Tata McGraw-Hill.

External links[edit]

• Patent problems
• The CPU Collection
• CPU-World
• The Gecko's CPU Library
• How Microprocessors Work
• IC Die Photography
• Great Microprocessors of the Past and Present
• Great moments in microprocessor history
• theDocuments
• MIPS, ARM and SPARC- an Architecture Comparison