Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...

8086 The 8086 (also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus (allo ...

i386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorspipelined x86 design as well as the first x86 chip to include more than one million transistors. It offered a large on-chip cache and an integrated

floating-point unit In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...

. A typical 50 MHz i486 executes around 40 million

instructions per second Instructions per second (IPS) is a measure of a computer's processor speed. For complex instruction set computers (CISCs), different instructions take different amounts of time, so the value measured depends on the instruction mix; even for co ...

(MIPS), reaching 50 MIPS peak performance. It is approximately twice as fast as the i386 or i286 per clock cycle. The i486's improved performance is thanks to its five-stage pipeline with all stages bound to a single cycle. The enhanced FPU unit on the chip was significantly faster than the i387 FPU per cycle. The intel 80387 FPU ("i387") was a separate, optional math coprocessor that was installed in a motherboard socket alongside the i386. The i486 was succeeded by the original Pentium.

History

The i486 was announced at Spring Comdex in April 1989. At the announcement, Intel stated that samples would be available in the third quarter and production quantities would ship in the fourth quarter. The first i486-based PCs were announced in late 1989. The first major update to the i486 design came in March 1992 with the release of the clock-doubled 486DX2 series. It was the first time that the CPU core clock frequency was separated from the

system bus A system bus is a single computer bus that connects the major components of a computer system, combining the functions of a data bus to carry information, an address bus to determine where it should be sent or read from, and a control bus to det ...

clock frequency by using a dual clock multiplier, supporting 486DX2 chips at 40 and 50 MHz. The faster 66 MHz 486DX2-66 was released that August. The fifth-generation Pentium processor launched in 1993, while Intel continued to produce i486 processors, including the triple-clock-rate 486DX4-100 with a 100 MHz clock speed and a L1 cache doubled to 16 KB. Earlier, Intel had decided not to share its 80386 and 80486 technologies with AMD. However, AMD believed that their technology sharing agreement extended to the 80386 as a derivative of the 80286. AMD reverse-engineered the 386 and produced the 40 MHz Am386DX-40 chip, which was cheaper and had lower power consumption than Intel's best 33 MHz version. Intel attempted to prevent AMD from selling the processor, but AMD won in court, which allowed it to establish itself as a competitor. AMD continued to create clones, releasing the first-generation Am486 chip in April 1993 with clock frequencies of 25, 33 and 40 MHz. Second-generation Am486DX2 chips with 50, 66 and 80 MHz clock frequencies were released the following year. The Am486 series was completed with a 120 MHz DX4 chip in 1995. AMD's long-running 1987 arbitration lawsuit against Intel was settled in 1995, and AMD gained access to Intel's 80486 microcode. This led to the creation of two versions of AMD's 486 processor - one reverse-engineered from Intel's microcode, while the other used AMD's microcode in a cleanroom development process. However, the settlement also concluded that the 80486 would be AMD's last Intel clone. Another 486 clone manufacturer was

Cyrix Cyrix Corporation was a microprocessor developer that was founded in 1988 in Richardson, Texas, as a specialist supplier of floating point units for 286 and 386 microprocessors. The company was founded by Tom Brightman and Jerry Rogers. In ...

, which was a fabless co-processor chip maker for 80286/386 systems. The first Cyrix 486 processors, the 486SLC and 486DLC, were released in 1992 and used the 80386 package. Both

Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...

-manufactured Cyrix processors were pin-compatible with 386SX/DX systems, which allowed them to become an upgrade option. However, these chips could not match the Intel 486 processors, having only 1 KB of cache memory and no built-in math coprocessor. In 1993, Cyrix released its own Cx486DX and DX2 processors, which were closer in performance to Intel's counterparts. Intel and Cyrix sued each other, with Intel going for

patent infringement Patent infringement is the commission of a prohibited act with respect to a patented invention without permission from the patent holder. Permission may typically be granted in the form of a license. The definition of patent infringement may v ...

and Cyrix going with

antitrust Competition law is the field of law that promotes or seeks to maintain market competition by regulating anti-competitive conduct by companies. Competition law is implemented through public and private enforcement. It is also known as antitrust ...

claims. In 1994 Cyrix won and dropped its antitrust claim. In 1995, both Cyrix and AMD began looking at a ready market for users wanting to upgrade their processors. Cyrix released a derivative 486 processor called the 5x86, based on the Cyrix M1 core, which was clocked up to 120 MHz and was an option for 486 Socket 3 motherboards. AMD released a 133 MHz Am5x86 upgrade chip, which was essentially an improved 80486 with double the cache and a quad multiplier that also worked with the original 486DX motherboards. Am5x86 was the first processor to use AMD's performance rating and was marketed as Am5x86-P75, with claims that it was equivalent to the Pentium 75. Kingston Technology launched a 'TurboChip' 486 system upgrade that used a 133 MHz Am5x86. Intel responded by making a

Pentium OverDrive The Pentium OverDrive was a microprocessor marketing brand name used by Intel, to cover a variety of consumer upgrade products sold in the mid-1990s. It was originally released for 486 motherboards, and later some Pentium sockets. Intel dropped the ...

upgrade chip for 486 motherboards, which was a modified Pentium core that ran up to 83 MHz on boards with a 25 or 33 MHz front-side bus clock. OverDrive wasn't popular due to speed and price. The 486 was declared obsolete as early as 1996, with a Florida school district's purchase of a fleet of 486DX4 machines in that year sparking controversy. New computers equipped with 486 processors in discount warehouses became scarce, and an IBM spokesperson called it a "dinosaur". Even after the Pentium series of processors gained a foothold in the market, however, Intel continued to produce 486 cores for industrial embedded applications. Intel discontinued production of i486 processors in late 2007.

Improvements

The

instruction set In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ...

of the i486 is very similar to the i386, with the addition of a few extra instructions, such as CMPXCHG, a compare-and-swap atomic operation, and XADD, a

fetch-and-add In computer science, the fetch-and-add CPU instruction (FAA) atomically increments the contents of a memory location by a specified value. That is, fetch-and-add performs the operation :increment the value at address by , where is a memory loc ...

atomic operation that returned the original value (unlike a standard ADD, which returns flags only). The i486's performance architecture is a vast improvement over the i386. It has an on-chip unified instruction and data cache, an on-chip

floating-point unit In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...

(FPU) and an enhanced bus interface unit. Due to the tight pipelining, sequences of simple instructions (such as ALU reg,reg and ALU reg,im) could sustain single-clock-cycle throughput (one instruction completed every clock). These improvements yielded a rough doubling in integer ALU performance over the i386 at the same clock rate. A 16 MHz i486 therefore had performance similar to a 33 MHz i386. The older design had to reach 50 MHz to be comparable with a 25 MHz i486 part.

Differences between i386 and i486

* An 8 KB on-chip (level 1) SRAM cache stores the most recently used instructions and data (16 KB and/or write-back on some later models). The

i386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorslevel 2 cache because i386 had no internal level 1 cache). * An enhanced external bus protocol to enable cache coherency and a new burst mode for memory accesses to fill a cache line of 16 bytes within five bus cycles. The 386 needed eight bus cycles to transfer the same amount of data. * Tightly coupled pipelining completes a simple instruction like ALU ''reg,reg'' or ALU ''reg,im'' every clock cycle (after a latency of several cycles). The i386 needed two clock cycles. * Integrated FPU (disabled or absent in SX models) with a dedicated local bus; together with faster algorithms on more extensive hardware than in the i387, this performed floating-point calculations faster than the

i386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorsi387 combination. * Improved MMU performance. * New instructions: XADD, BSWAP, CMPXCHG, INVD, WBINVD, INVLPG. Just as in the i386, a flat 4 GB memory model could be implemented. All "segment selector" registers could be set to a neutral value in

protected mode In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as virtual memory, paging and safe multi-taskin ...

, or to zero in

real mode Real mode, also called real address mode, is an operating mode of all x86-compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20- bit ...

, and using only the 32-bit "offset registers" (x86-terminology for general CPU registers used as address registers) as a linear 32-bit virtual address bypassing the segmentation logic. Virtual addresses were then normally mapped onto physical addresses by the paging system except when it was disabled. (''Real'' mode had no ''virtual'' addresses.) Just as with the i386, circumventing memory segmentation could substantially improve performance for some operating systems and applications. On a typical PC motherboard, either four matched 30-pin (8-bit)

SIMM A SIMM (single in-line memory module) is a type of memory module containing random-access memory used in computers from the early 1980s to the early 2000s. It differs from a dual in-line memory module (DIMM), the most predominant form of memo ...

s or one 72-pin (32-bit) SIMM per bank were required to fit the i486's

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32- bit units. Compared to smaller bit widths, 32-bit computers can perform large calculati ...

data bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ...

. The

address bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This e ...

used 30-bits (A31..A2) complemented by four byte-select pins (instead of A0,A1) to allow for any 8/16/32-bit selection. This meant that the limit of directly addressable physical memory was 4

gigabyte The gigabyte () is a multiple of the unit byte for digital information. The prefix '' giga'' means 109 in the International System of Units (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is GB. This definit ...

s as well (2³⁰ ''32-bit'' words = 2³² ''8-bit'' words).

Models

Intel offered several suffixes and variants (see table). Variants include: * '' Intel RapidCAD'': a specially packaged Intel 486DX and a dummy

floating-point unit In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...

(FPU) designed as pin-compatible replacements for an

i386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors 80387 x87 is a floating-point-related subset of the x86 architecture instruction set. It originated as an extension of the 8086 instruction set in the form of optional floating-point coprocessors that worked in tandem with corresponding x86 CPUs. These ...

FPU. * ''i486SL-NM'': i486SL based on i486SX. * '' i487SX (P23N)'': i486DX with one extra pin sold as an FPU upgrade to i486SX systems; When the i487SX was installed, it ensured that an i486SX was present on the motherboard but disabled it, taking over all of its functions. * '' i486 OverDrive (P23T/P24T)'': i486SX, i486SX2, i486DX2 or i486DX4. Marked as upgrade processors, some models had different pinouts or voltage-handling abilities from "standard" chips of the same speed. Fitted to a coprocessor or "OverDrive" socket on the motherboard, they worked the same as the i487SX. The maximal internal clock frequency (on Intel's versions) ranged from 16 to 100 MHz. The 16 MHz i486SX model was used by Dell Computers. One of the few i486 models specified for a 50 MHz bus (486DX-50) initially had overheating problems and was moved to the 0.8-

micrometer Micrometer can mean: * Micrometer (device), used for accurate measurements by means of a calibrated screw * American spelling of micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures; ...

fabrication process. However, problems continued when the 486DX-50 was installed in local-bus systems due to the high bus speed, making it unpopular with mainstream consumers. Local-bus video was considered a requirement at the time, though it remained popular with users of EISA systems. The 486DX-50 was soon eclipsed by the clock-doubled i486DX2, which although running the internal CPU logic at twice the external bus speed (50 MHz), was nevertheless slower because the external bus ran at only 25 MHz. The i486DX2 at 66 MHz (with 33 MHz external bus) was faster than the 486DX-50, overall. More powerful i486 iterations such as the OverDrive and

DX4 IntelDX4 is a clock-tripled i486 microprocessor with 16-kB Level 1 cache.http://www.pld.ttu.ee/~prj/486dev.pdf Intel named it DX4 (rather than ''DX3'') as a consequence of litigation with AMD over trademarks. The product was officially na ...

were less popular (the latter available as an OEM part only), as they came out after Intel had released the next-generation Pentium processor family. Certain steppings of the DX4 also officially supported 50 MHz bus operation, but it was a seldom-used feature. : *''WT'' = write-through cache strategy, ''WB'' = write-back cache strategy

Other makers of 486-like CPUs

Processors compatible with the i486 were produced by companies such as IBM,

Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...

, AMD,

Cyrix Cyrix Corporation was a microprocessor developer that was founded in 1988 in Richardson, Texas, as a specialist supplier of floating point units for 286 and 386 microprocessors. The company was founded by Tom Brightman and Jerry Rogers. In ...

, UMC, and

STMicroelectronics STMicroelectronics N.V. commonly referred as ST or STMicro is a Dutch multinational corporation and technology company of French-Italian origin headquartered in Plan-les-Ouates near Geneva, Switzerland and listed on the French stock market. ST ...

(formerly SGS-Thomson). Some were clones (identical at the microarchitectural level), others were clean room implementations of the Intel instruction set. (IBM's multiple-source requirement was one of the reasons behind its x86 manufacturing since the 80286.) The i486 was, however, covered by many Intel patents, including from the prior i386. Intel and IBM had 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. AMD produced several clones using a 40 MHz bus (486DX-40, 486DX/2-80, and 486DX/4-120) which had no Intel equivalent, as well as a part specified for 90 MHz, using a 30 MHz external clock, that was sold only to OEMs. The fastest running i486-compatible CPU, the Am5x86, ran at 133 MHz and was released by AMD in 1995. 150 MHz and 160 MHz parts were planned but never officially released. Cyrix made a variety of i486-compatible processors, positioned at the cost-sensitive desktop and low-power (laptop) markets. Unlike AMD's 486 clones, the Cyrix processors were the result of clean-room reverse engineering. Cyrix's early offerings included the 486DLC and 486SLC, two hybrid chips that plugged into 386DX or SX sockets respectively, and offered 1 KB of cache (versus 8 KB for the then-current Intel/AMD parts). Cyrix also made "real" 486 processors, which plugged into the i486's socket and offered 2 or 8 KB of cache. Clock-for-clock, the Cyrix-made chips were generally slower than their Intel/AMD equivalents, though later products with 8 KB caches were more competitive, albeit late to market. The

Motorola 68040 The Motorola 68040 ("''sixty-eight-oh-forty''") is a 32-bit microprocessor in the Motorola 68000 series, released in 1990. It is the successor to the 68030 and is followed by the 68060, skipping the 68050. In keeping with general Motorola na ...

, while not i486 compatible, was often positioned as its equivalent in features and performance. Clock-for-clock basis the

Motorola 68040 The Motorola 68040 ("''sixty-eight-oh-forty''") is a 32-bit microprocessor in the Motorola 68000 series, released in 1990. It is the successor to the 68030 and is followed by the 68060, skipping the 68050. In keeping with general Motorola na ...

could significantly outperform the Intel chip. However, the i486 had the ability to be clocked significantly faster without overheating.

Motorola 68040 The Motorola 68040 ("''sixty-eight-oh-forty''") is a 32-bit microprocessor in the Motorola 68000 series, released in 1990. It is the successor to the 68030 and is followed by the 68060, skipping the 68050. In keeping with general Motorola na ...

performance lagged behind the later production i486 systems.

Motherboards and buses

Early i486-based computers were equipped with several

ISA Isa or ISA may refer to: Places * Isa, Amur Oblast, Russia * Isa, Kagoshima, Japan * Isa, Nigeria * Isa District, Kagoshima, former district in Japan * Isa Town, middle class town located in Bahrain * Mount Isa, Queensland, Australia * Mount ...

slots (using an emulated PC/AT-bus) and sometimes one or two

8-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses ...

-only slots (compatible with the PC/XT-bus). Many motherboards enabled overclocking of these from the default 6 or 8 MHz to perhaps 16.7 or 20 MHz (half the i486 bus clock) in several steps, often from within the BIOS setup. Especially older peripheral cards normally worked well at such speeds as they often used standard MSI chips instead of slower (at the time) custom VLSI designs. This could give significant performance gains (such as for old video cards moved from a 386 or 286 computer, for example). However, operation beyond 8 or 10 MHz could sometimes lead to stability problems, at least in systems equipped with SCSI or sound cards. Some motherboards came equipped with a

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32- bit units. Compared to smaller bit widths, 32-bit computers can perform large calculati ...

EISA bus that was backward compatible with the ISA-standard. EISA offered attractive features such as increased bandwidth, extended addressing, IRQ sharing, and card configuration through software (rather than through jumpers, DIP switches, etc.) However, EISA cards were expensive and therefore mostly employed in servers and workstations. Consumer desktops often used the simpler, faster

VESA Local Bus The VESA Local Bus (usually abbreviated to VL-Bus or VLB) is a short-lived expansion bus introduced during the i486 generation of x86 IBM-compatible personal computers. Created by VESA (Video Electronics Standards Association), the VESA Local ...

(VLB). Unfortunately prone to electrical and timing-based instability; typical consumer desktops had ISA slots combined with a single VLB slot for a video card. VLB was gradually replaced by PCI during the final years of the i486 period. Few

Pentium class The Pentium (also referred to as P5, its microarchitecture, or i586) is a fifth generation, 32-bit x86 microprocessor that was introduced by Intel on March 22, 1993, as the very first CPU in the Pentium brand. It was instruction set compatible ...

motherboards had VLB support as VLB was based directly on the i486 bus; much different from the P5 Pentium-bus. ISA persisted through the P5 Pentium generation and was not completely displaced by PCI until the Pentium III era. Late i486 boards were normally equipped with both PCI and ISA slots, and sometimes a single VLB slot. In this configuration, VLB or PCI throughput suffered depending on how buses were bridged. Initially, the VLB slot in these systems was usually fully compatible only with video cards (fitting as "VESA" stands for '' Video Electronics Standards Association''); VLB-IDE, multi I/O, or SCSI cards could have problems on motherboards with PCI slots. The VL-Bus operated at the same clock speed as the i486-bus (basically a local bus) while the PCI bus also usually depended on the i486 clock but sometimes had a divider setting available via the BIOS. This could be set to 1/1 or 1/2, sometimes even 2/3 (for 50 MHz CPU clocks). Some motherboards limited the PCI clock to the specified maximum of 33 MHz and certain network cards depended on this frequency for correct bit-rates. The ISA clock was typically generated by a divider of the CPU/VLB/PCI clock. One of the earliest complete systems to use the i486 chip was the Apricot VX FT, produced by British hardware manufacturer Apricot Computers. Even overseas in the United States it was popularized as "The World's First 486". Later i486 boards supported

Plug-And-Play In computing, a plug and play (PnP) device or computer bus is one with a specification that facilitates the recognition of a hardware component in a system without the need for physical device configuration or user intervention in resolving resou ...

, a specification designed by

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washi ...

that began as a part of

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturi ...

to make component installation easier for consumers.

Obsolescence

The

AMD Am5x86 The Am5x86 processor is an x86-compatible CPU announced in November of 1995 by AMD for use in 486-class computer systems. It began shipping in December of 1995, with a base price of $93 per unit in bulk quantities. Before being released, it wa ...

and

Cyrix Cx5x86 The Cyrix 5x86 was a line of x86 microprocessors designed by Cyrix and released on June 5 of 1995. Cyrix, being a fabless company, had the chips manufactured by IBM. The line came out about 5 months before the more famous Cyrix 6x86. The Cyri ...

were the last i486 processors often used in late-generation i486 motherboards. They came with PCI slots and 72-pin SIMMs that were designed to run

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturi ...

, and also used for 80486 motherboards upgrades. While the

Cyrix Cx5x86 The Cyrix 5x86 was a line of x86 microprocessors designed by Cyrix and released on June 5 of 1995. Cyrix, being a fabless company, had the chips manufactured by IBM. The line came out about 5 months before the more famous Cyrix 6x86. The Cyri ...

faded when the Cyrix 6x86 took over, the

AMD Am5x86 The Am5x86 processor is an x86-compatible CPU announced in November of 1995 by AMD for use in 486-class computer systems. It began shipping in December of 1995, with a base price of $93 per unit in bulk quantities. Before being released, it wa ...

remained important given AMD K5 delays. Computers based on the i486 remained popular through the late 1990s, serving as low-end processors for entry-level PCs. Production for traditional desktop and laptop systems ceased in 1998, when Intel introduced the

Celeron Celeron is Intel's brand name for low-end IA-32 and x86-64 computer microprocessor models targeted at low-cost personal computers. Celeron processors are compatible with IA-32 software. They typically offer less performance per clock speed co ...

brand, though it continued to be produced for embedded systems through the late 2000s. In the general-purpose desktop computer role, i486-based machines remained in use into the early 2000s, especially as Windows 95 through 98 and

Windows NT 4.0 Windows NT 4.0 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It is the direct successor to Windows NT 3.51, which was released to manufacturing on July 31, 1996, and then to retail ...

were the last Microsoft operating systems to officially support i486-based systems.

Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was the direct successor to Windows NT 4.0, and was released to manufacturing on December 15, 1999, and was offici ...

could run on a i486-based machine, although with a less than optimal performance, due to the minimum hardware requirement of a Pentium processor. However, as they were overtaken by newer operating systems, i486 systems fell out of use except for

backward compatibility Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especiall ...

with older programs (most notably games), especially given problems running on newer operating systems. However,

DOSBox DOSBox is a free and open-source emulator which runs software for MS-DOS compatible disk operating systems—primarily video games. It was first released in 2002, when DOS technology was becoming obsolete. Its adoption for running DOS games i ...

was available for later operating systems and provides emulation of the i486 instruction set, as well as full compatibility with most DOS-based programs. The i486 was eventually overtaken by the Pentium for

personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...

applications, although Intel continued production for use in embedded systems. In May 2006, Intel announced that production of the i486 would stop at the end of September 2007.

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...

6 will likely be the last Linux kernel to support i486.

Notes

References

External links

Intel486 datasheets
*
Low power SX and DX with variable freq. Dec 1992
*
EMBEDDED ULTRA-LOW POWER Intel 486 SX
*
Embedded Write-Back Enhanced Intel DX4. Oct 1995

Intel i486 DX images and descriptions at cpu-collection.de

Die photo of Intel 386DX
{{DEFAULTSORT:Intel I486 Computer-related introductions in 1989

486 __NOTOC__ Year 486 (Roman numerals, CDLXXXVI) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Basilius and Longinus (or, less freq ...

32-bit microprocessors

History

Improvements

Differences between i386 and i486

Models

Other makers of 486-like CPUs

Motherboards and buses

Obsolescence

See also

Notes

References

External links