Central processing unit
The exposed die of an Intel 80486DX2 microprocessor.
|Produced:||From 1989 to 2007|
|Max CPU clock:||16 MHz to 133 MHz|
|FSB speeds:||16 MHz to 50 MHz|
|Min feature size:||0. Texas Instruments ( better known in the electronics industry (and popularly as TI, is an American company based in Dallas, Texas, USA The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. In Personal computers the Front Side Bus ( FSB) is the bus that carries data between the CPU and the northbridge. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. 8 µm|
|Instruction set:||x86 (i386)|
The Intel486 brand encompasses Intel's family of i486 (incl. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre An instruction set is a list of all the instructions and all their variations that a processor can execute See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal A multi-core processor (or chip-level multiprocessor, CMP) combines two or more independent cores into a single package composed of a single Integrated Socket 1 was the second of a series of standard sockets created by Intel into which various X86 Microprocessors were plugged Socket 2 was one of the series of sockets into which various X86 Microprocessors were plugged Socket 3 was a type of CPU socket into which various X86 Microprocessors were inserted i487) CPUs - the second generation of 32-bit x86 microprocessors, and the first truly pipelined x86 design. The range of Integer values that can be stored in 32 bits is 0 through 4294967295 or −2147483648 through 2147483647 using Two's complement encoding See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated In Computing, a pipeline is a set of data processing elements connected in series so that the output of one element is the input of the next one Their predecessor was the Intel386, the very first 32-bit x86 processor. The first line of 486 processors was introduced in 1989 containing 1. 2 million transistors (800 nanometer scale). The 800 nanometer (800 nm or 08 µm) process refers to the level of semiconductor process technology that was reached in the 1989-1990 timeframe by most leading The i486 was so named without the usual 80-prefix, because of a court ruling that prohibited trademarking numbers (like 80486). Intel dropped number-based naming altogether with the successor to the i486 – the Pentium processor. The Pentium brand refers to Intel 's single-core x86 Microprocessor based on the P5 fifth-generation Microarchitecture.
The instruction set of the i486 is very similar to its predecessor, the Intel 80386, with the addition of only a few extra instructions, such as CMPXCHG which executes the Compare-and-swap atomic operation and the XADD which executes the Fetch-and-add atomic operation. An instruction set is a list of all the instructions and all their variations that a processor can execute In Computer science, the compare-and-swap CPU instruction (" CAS " (or the Compare & Exchange - CMPXCHG instruction in the X86 and In Computer science, the fetch-and-add CPU instruction is a special instruction that atomically modifies the contents of a memory location Though many atomic instructions have existed since the 8086/8088, they did not correspond to the atomic instructions implemented in certain RISC processors, which made it harder to port some applications from these processors. The 8086 is a 16-bit Microprocessor chip designed by Intel and introduced on the market in 1978 which gave rise to the X86 architecture The Intel 8088 is an Intel X86 Microprocessor based on the 8086, with 16- Bit registers and an 8-bit external Data bus
From a performance point of view, the architecture of the i486 is a vast improvement over the 80386. It has an on-chip unified instruction and data cache, an on-chip floating-point unit (FPU), and an enhanced bus interface unit. A floating point unit (FPU is a part of a Computer system specially designed to carry out operations on Floating point numbers In Computer architecture, a bus is a subsystem that transfers data between computer components inside a Computer or between computers In addition, simple instructions (such as ALU reg,reg) has a single clock troughput. These improvements yield a rough doubling in performance over the 386 at the same clock rate. The clock rate is the fundamental rate in cycles per second (measured in Hertz) at which a Computer performs its most basic operations such as adding two A 386 (or 286) chip therefore has to reach 50 MHz to be comparable with low end parts in the 486 series. The Intel 286, introduced on February 1, 1982, (originally named 80286, and also called iAPX 286 in the programmer's manual
The 486 has a 32-bit data bus and a 32-bit address bus. In Computer architecture, a bus is a subsystem that transfers data between computer components inside a Computer or between computers An address bus is a Computer bus, controlled by CPUs or DMA -capable Peripherals for specifying the Physical addresses of computer This required either four matched 30-pin SIMMs or one 72-pin SIMM on a typical PC motherboard. A SIMM, or single in-line memory module, is a type of memory module containing Random access memory used in Computers from the early 1980s to the late 1990s A motherboard is the central or primary Printed circuit board (PCB making up a complex electronic system such as a modern Computer or Laptop The 32-bit address bus means that 4 GiB of memory can be directly addressed. A gibibyte (a contraction of gi ga bi nary byte) is a unit of Information or Computer storage, abbreviated GiB.
The Intel project manager for the 80486 was Pat Gelsinger. Pat Gelsinger was the first Chief Technology Officer of Intel Corporation.
In May 2006 Intel announced that production of the 80486 would cease at the end of September 2007.  Although the chip had long been obsolete for personal computer applications, Intel had continued production for use in embedded systems. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints The 80486 was able to compute at up to 41 million instructions per second. Instructions per second (IPS is a measure of a Computer 's processor speed 
There are several suffixes and variants including:
Maximum specified internal clock rates ranged from 16 to 133 MHz (16, 20, 25, 33, 40, 50, 66, 75, 100, 120, and 133 MHz). The only 486 specified for a 50 MHz bus had reliability problems with many boards and components because of this high bus speed, making it rather unpopular. It was soon replaced by the clock-doubled i486DX2 which instead ran the CPU logic at twice the external bus speed. The Intel 's i486DX2 is a CPU produced by Intel that was introduced in 1989. A slower i486DX2-50 was also sold, with a bus speed of 25MHz. More powerful 486 iterations such as the OverDrive and DX4 were less popular, as they came out after Intel had released the next generation Pentium. The Pentium brand refers to Intel 's single-core x86 Microprocessor based on the P5 fifth-generation Microarchitecture.
The 486DX2 66 MHz was the most widespread high-end 486 version. For many players of video games during the early and mid 1990s, towards the end of the MS-DOS gaming era, it was often coupled with 8 - 16 MB RAM and a VLB video card. A video game is a Game that involves interaction with a User interface to generate visual feedback on a video device. MS-DOS (short for M icro' s' oft D isk O perating S ystem is an Operating system commercialized by Microsoft. The VESA Local Bus (usually abbreviated to VL-Bus or VLB) was mostly used in personal computers This configuration was capable of running every title available for several years after its release, making it a "sweet spot" in CPU performance and longevity. A sweet spot is a place often numerical as opposed to physical where a combination of factors suggest a particularly suitable solution The introduction of 3D graphics spelled the end of the 486's reign, because of its heavy use of floating point calculations and the need for faster cache and more memory bandwidth. In Computing, floating point describes a system for numerical representation in which a string of digits (or Bits represents a Real number. Memory bandwidth is the rate at which data can be read from or stored into a Semiconductor memory by a processor. Developers also began to target the Pentium almost exclusively with assembly optimizations (e. See the terminology section below for information regarding inconsistent use of the terms assembly and assembler g. Quake). Quake is a First-person shooter Computer game that was released by Id Software on June 22, 1996.
486 compatible processors have been produced by other companies such as IBM, Texas Instruments, AMD, Cyrix, UMC, and Chips and Technologies. International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology Texas Instruments ( better known in the electronics industry (and popularly as TI, is an American company based in Dallas, Texas, USA Cyrix was a CPU manufacturer that began in 1978 in Richardson Texas as a specialist supplier of high-performance math co-processors for 286 and UMC ( United Microelectronics Corporation) was founded as Taiwan's first Semiconductor company in 1980 as a spin-off of the government-sponsored institute ITRI Chips and Technologies ( C&T) was the first Fabless semiconductor company, a model developed by its founder Gordon Campbell Some are near duplicates in terms of specifications and performance, some are not. The 486 was, however, covered by many of Intel's 386 patents as well as some of its own. Intel and IBM have broad cross-licenses of these patents, and AMD was granted rights to the relevant patents in the 1995 settlement of a lawsuit between the companies. 
The fastest running 486 CPU, the Am5x86, was released by AMD in 1995. The Am5x86 processor is an X86 -compatible CPU introduced in 1995 by AMD for use in 486 -class Computer systems
Early 486 machines were equipped with several ISA-slots (Industry Standard Architecture) which was noting but alternatively named 16-bit AT-bus compatible slots (plus one or two 8-bit-only PC/XT slots). Industry Standard Architecture (in practice almost always shortened to ISA) was a Computer bus standard for IBM compatible computers Eight-bit CPUs normally use an 8-bit data bus and a 16-bit address bus which means that their Address space is limited to 64 KBs This is not a "natural Many motherboards enabled overclocking of these up from the default 6 or 8 MHz to perhaps 16. A motherboard is the central or primary Printed circuit board (PCB making up a complex electronic system such as a modern Computer or Laptop 5 or 20 MHz (half the i486 bus clock) in a number of steps, often from within the BIOS setup. In Computing, the BIOS (ˈbaɪoʊs Especially older peripheral cards normally worked well at such speeds as they often used standard MSI chips instead of (the at the time) slower custom VLSI designs. This could give significant performance gains (such as for old video cards moved from a 386 or 286 computer, for example).
Some motherboards came equipped with a 32 bit version of the ISA-standard called EISA (Extended Industry Standard Architecture). The Extended Industry Standard Architecture (in practice almost always shortened to EISA and frequently pronounced "eee-suh" is a bus standard for IBM compatible However, EISA were rather quickly supplanted by the simpler but faster VLB (VESA Local Bus) intended for fast video cards and hard drive controllers. The VESA Local Bus (usually abbreviated to VL-Bus or VLB) was mostly used in personal computers PCI (Peripheral Component Interconnect) then began gradually replacing VLB. The Peripheral Component Interconnect, or PCI Standard (commonly PCI) specifies a Computer bus for attaching peripheral devices to a Computer
Mature 486 boards were normally equipped with both PCI- and ISA-slots, and sometimes a single VLB-slot as well. In this configuration VLB sometimes suffered performance-wise and was usually only compatible with video cards (VLB-IDE, multi I/O, or SCSI cards often had problems on motherboards with PCI slots). The VL-Bus operated at the same clock speed as the i486-bus (basically being a local 486-bus). The PCI bus also usually depended on the i486 clock but had a divider. This could be set to 1/1, but some boards limited the PCI clock to the specified maximum of 33 MHz (some network cards assumed 33MHz and would produce erroneous bit-rates in an overclocked slot). The ISA clock was either generated by a separate clock generator or by a divider of the VLB/PCI clock.
One of the earliest complete systems to use the 80486 chip was the Apricot VX FT, produced by United Kingdom hardware manufacturer Apricot Computers. Apricot Computers was a British manufacturer of business Personal computers originally founded in 1965 as "Applied Computer Techniques" (ACT Even overseas in the United States it drew attention as "The World's First 486" in a popular September 1989 issue of Byte magazine (shown right). Byte magazine was an influential Microcomputer magazine in the late 1970s and throughout the 1980s because of its wide-ranging editorial coverage
Later 486 boards also supported Plug-And-Play, the Microsoft technology that began as a part of Windows 95 designed to make component installation easier for consumers. Plug-and-play is a computer feature that allows the addition of a new device normally a Peripheral, without requiring reconfiguration or manual installation of Device Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer Windows 95 is a consumer-oriented Graphical user interface -based Operating system.
This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. The Free On-line Dictionary of Computing ( FOLDOC) is an online searchable encyclopedic Dictionary of Computing subjects The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software