A central processing unit (CPU), also called a central processor, main processor, or just processor, is the most important processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, logic, controlling, and input/output (I/O) operations. This role contrasts with that of external components, such as main memory and I/O circuitry, and specialized coprocessors such as graphics processing units (GPUs).
A microprocessor is a computer processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, and control circuitry required to perform the functions of a computer's central processing unit (CPU). The IC is capable of interpreting and executing program instructions and performing arithmetic operations. The microprocessor is a multipurpose, clock-driven, register-based, digital integrated circuit that accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output. Microprocessors contain both combinational logic and sequential digital logic, and operate on numbers and symbols represented in the binary number system.
In processor design, microcode serves as an intermediary layer situated between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer, also known as its machine code. It consists of a set of hardware-level instructions that implement the higher-level machine code instructions or control internal finite-state machine sequencing in many digital processing components. While microcode is utilized in Intel and AMD general-purpose CPUs in contemporary desktops and laptops, it functions only as a fallback path for scenarios that the faster hardwired control unit is unable to manage.
A minicomputer, or colloquially mini, is a type of smaller general-purpose computer developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, The New York Times suggested a consensus definition of a minicomputer as a machine costing less than US$25,000, with an input-output device such as a teleprinter and at least four thousand words of memory, that is capable of running programs in a higher level language, such as Fortran or BASIC.
Programmed Data Processor (PDP), referred to by some customers, media and authors as "Programmable Data Processor," is a term used by the Digital Equipment Corporation from 1957 to 1990 for several lines of minicomputers.
The PDP-8 is a family of 12-bit minicomputers that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units sold during the model's lifetime. Its basic design follows the pioneering LINC but has a smaller instruction set, which is an expanded version of the PDP-5 instruction set. Similar machines from DEC are the PDP-12 which is a modernized version of the PDP-8 and LINC concepts, and the PDP-14 industrial controller system.
The CDC 6600 was the flagship of the 6000 series of mainframe computer systems manufactured by Control Data Corporation. Generally considered to be the first successful supercomputer, it outperformed the industry's prior recordholder, the IBM 7030 Stretch, by a factor of three. With performance of up to three megaFLOPS, the CDC 6600 was the world's fastest computer from 1964 to 1969, when it relinquished that status to its successor, the CDC 7600.
A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-only. In computer architecture, registers are typically addressed by mechanisms other than main memory, but may in some cases be assigned a memory address e.g. DEC PDP-10, ICT 1900.
4-bit computing is the use of computer architectures in which integers and other data units are 4 bits wide. 4-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses of that size. A group of four bits is also called a nibble and has 24 = 16 possible values, with a range of 0 to 15.
In computing, a memory address is a reference to a specific memory location in memory used by both software and hardware. These addresses are fixed-length sequences of digits, typically displayed and handled as unsigned integers. This numerical representation is based on the features of CPU, as well programming language constructs that treat the memory like an array.
Addressing modes are an aspect of the instruction set architecture in most central processing unit (CPU) designs. The various addressing modes that are defined in a given instruction set architecture define how the machine language instructions in that architecture identify the operand(s) of each instruction. An addressing mode specifies how to calculate the effective memory address of an operand by using information held in registers and/or constants contained within a machine instruction or elsewhere.
In computer architecture, 36-bit integers, memory addresses, or other data units are those that are 36 bits wide. Also, 36-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size. 36-bit computers were popular in the early mainframe computer era from the 1950s through the early 1970s.
The PDP-5 was Digital Equipment Corporation's first 12-bit computer, introduced in 1963.
The Signetics 2650 was an 8-bit microprocessor introduced in July 1975. According to Adam Osborne's book An Introduction to Microprocessors Vol 2: Some Real Products, it was "the most minicomputer-like" of the microprocessors available at the time. A combination of missing features and odd memory access limited its appeal, and the system saw little use in the market.
Am2900 is a family of integrated circuits (ICs) created in 1975 by Advanced Micro Devices (AMD). They were constructed with bipolar devices, in a bit-slice topology, and were designed to be used as modular components each representing a different aspect of a computer control unit (CCU). By using the bit slicing technique, the Am2900 family was able to implement a CCU with data, addresses, and instructions to be any multiple of 4 bits by multiplying the number of ICs. One major problem with this modular technique was that it required a larger number of ICs to implement what could be done on a single CPU IC. The Am2901 chip included an arithmetic logic unit (ALU) and 16 4-bit processor register slices, and was the "core" of the series. It could count using 4 bits and implement binary operations as well as various bit-shifting operations. The Am2909 was a 4-bit-slice address sequencer that could generate 4-bit addresses on a single chip, and by using n of them, it was able to generate 4n-bit addresses. It had a stack that could store a microprogram counter up to 4 nest levels, as well as a stack pointer.
DECmate was the name of a series of PDP-8-compatible computers produced by the Digital Equipment Corporation in the late 1970s and early 1980s. All of the models used an Intersil 6100 or Harris 6120 microprocessor which emulated the 12-bit DEC PDP-8 CPU. They were text-only and used the OS/78 or OS/278 operating systems, which were extensions of OS/8 for the PDP-8. Aimed at the word processing market, they typically ran the WPS-8 word-processing program. Later models optionally had Intel 8080 or Z80 microprocessors which allowed them to run CP/M. The range was a development of the VT78 which was introduced in July 1977.
LINC-8 is the name of a minicomputer manufactured by Digital Equipment Corporation between 1966 and 1969. It combines a LINC computer with a PDP-8 in one cabinet, thus being able to run programs written for either of the two architectures.
The Intersil 6100, or IM6100, is a single-chip microprocessor implementation of the 12-bit PDP-8 instruction set, along with a range of peripheral support and memory ICs developed by Intersil in the mid-1970s. It was sometimes referred to as the CMOS-PDP8. Since it was also produced by Harris Corporation, it was also known as the Harris HM-6100. The Intersil 6100 was introduced in the second quarter of 1975, and the Harris version in 1976.
An instruction set architecture (ISA) is an abstract model of a computer, also referred to as computer architecture. A realization of an ISA is called an implementation. An ISA permits multiple implementations that may vary in performance, physical size, and monetary cost ; because the ISA serves as the interface between software and hardware. Software that has been written for an ISA can run on different implementations of the same ISA. This has enabled binary compatibility between different generations of computers to be easily achieved, and the development of computer families. Both of these developments have helped to lower the cost of computers and to increase their applicability. For these reasons, the ISA is one of the most important abstractions in computing today.
In computer architecture, 16-bit integers, memory addresses, or other data units are those that are 16 bits wide. Also, 16-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size. 16-bit microcomputers are microcomputers that use 16-bit microprocessors.
