Wikipedia

i486

(Redirected from80486)

TheIntel486,officially namedi486and also known as80486,is amicroprocessorintroduced in 1989. It is a higher-performance follow-up to theIntel 386.It represents the fourth generation ofbinary compatibleCPUs following the8086of 1978, theIntel 80286of 1982, and 1985'si386.

i486
The exposed die of an Intel 486DX2
General information
LaunchedApril 10, 1989[2]
DiscontinuedSeptember 28, 2007[1]
Designed byIntel,withPat Gelsingeras chief architect
Common manufacturer
Performance
Max.CPUclock rate16 to 100 MHz[a]
FSBspeeds16 MHz to 50 MHz
Data width32 bits[3]
Address width32 bits[3]
Virtual address width32 bits (linear); 46 bits (logical)[3]
Cache
L1cache8 KB to 16 KB
Architecture and classification
Technology node1 μm to 600 nm
Instruction setx86-16,IA-32includingx87(except for "SX"models)
Physical specifications
Transistors
  • 1.2[2]–1.6 million
Co-processorIntel 80487SX
Package
Socket
History
PredecessorIntel 386
SuccessorPentium/i586 (P5)
Support status
Unsupported

It was the first tightly-pipelined[c]x86design as well as the first x86 chip to include more than one million transistors. It offered a large on-chipcacheand an integratedfloating-point unit.When it was announced, the initial performance was originally published between 15 and 20VAX MIPS,between 37,000 and 49,000dhrystones per second,and between 6.1 and 8.2 double-precisionmegawhetstones per secondfor both 25 and 33 MHz version.[2]A typical 50 MHz i486 executes 41 millioninstructions per secondDhrystone MIPS andSPEC integerrating of 27.9.[4]It is approximately twice as fast as the i386 or i286 perclock 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 thei387FPU per cycle. The i387 FPU was a separate, optional math coprocessor installed in a motherboard socket alongside the i386.[5]

The i486 was succeeded by theoriginal Pentium.Orders were discontinued for the i486 on March 30, 2007 and the last shipments were on September 28, 2007.[1]

History

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The concept of this microprocessor generation was discussed with Pat Gelsinger andJohn Crawfordshortly after the release of386 processorin 1985. The team started the computer simulation in early 1987. They finalized the logic and microcode function during 1988. The team finalized the database in February 1989 until thetape outon March 1. They received the first silicon from the fabrication on March 20.[6]

The i486 was announced at SpringComdexin April 10, 1989.[2]At the announcement, Intel stated that samples would be available in the third quarter and production quantities would ship in the fourth quarter.[7]The first i486-based PCs were announced in late 1989.[8]

In fall of 1991, Intel introduced the 50 MHz i486 DX using the three layer800 nm processCHMOS-Vtechnology. They were available for US$665 in 1,000-unit quantities.[9]

In that season, Intel introduced low-power 25 MHz Intel486 DX microprocessor. This one was available for US$471. Also, there were low-power 16, 20, and 25 MHz Intel486 SX microprocessors. They were available at $235, $266, and $366 for these frequency range respectively. All pricing were in quantities of 1,000 pieces. These low-power microprocessors have power consumption reduced by 50–75% compared to similar regular versions of these CPUs.[10]

The first major update to the i486 design came in March 1992 with the release of the clock-doubled486DX2series.[11]It was the first time that the CPU core clock frequency was separated from thesystem busclock 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.[11]

The fifth-generationPentiumprocessor launched in 1993, while Intel continued to produce i486 processors, including the triple-clock-rate486DX4-100with a 100 MHz clock speed and a L1 cache doubled to 16 KB.[11]

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.[11]AMD reverse-engineered the 386 and produced the 40 MHzAm386DX-40chip, which was cheaper and had lower power consumption than Intel's best 33 MHz version.[11]Intel attempted to prevent AMD from selling the processor, but AMD won in court, which allowed it to establish itself as a competitor.[12]

AMD continued to create clones, releasing the first-generationAm486chip 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.[11]The Am486 series was completed with a 120 MHz DX4 chip in 1995.[11]

AMD's long-running 1987 arbitration lawsuit against Intel was settled in 1995, and AMD gained access to Intel's 80486 microcode.[11]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 aclean-room designprocess. However, the settlement also concluded that the 80486 would be AMD's last Intel clone.[11]

Another 486 clone manufacturer wasCyrix,which was afablessco-processor chip maker for 80286/386 systems. The firstCyrix 486processors, the 486SLC and 486DLC, were released in 1992 and used the 80386 package.[11]BothTexas Instruments-manufactured Cyrix processors were pin-compatible with 386SX/DX systems, which allowed them to become an upgrade option.[12]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 filing forpatent infringement,and Cyrix forantitrustclaims. In 1994, Cyrix won the patent infringement case and dropped its antitrust claim.[11]

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 the5x86,based on the Cyrix M1 core, which was clocked up to 120 MHz and was an option for 486 Socket 3 motherboards.[11][12]AMD released a 133 MHzAm5x86upgrade chip, which was essentially an improved 80486 with double the cache and a quad multiplier that also worked with the original 486DX motherboards.[11]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.[12]Kingston Technologylaunched a "TurboChip" 486 system upgrade that used a 133 MHz Am5x86.[11]

Intel responded by making aPentium OverDriveupgrade 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.[11]New computers equipped with 486 processors in discount warehouses became scarce, and anIBMspokesperson called it a "dinosaur".[13]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.[1][11]

Improvements

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The 486DX2 architecture
i486 registers
31 ... 15 ... 07 ... 00 (bit position)
Main registers(8/16/32 bits)
EAX AH AL Aregister
EBX BH BL Bregister
ECX CH CL Cregister
EDX DH DL Dregister
Index registers(16/32 bits)
ESI SI SourceIndex
EDI DI DestinationIndex
EBP BP BasePointer
ESP SP StackPointer
Program counter(16/32 bits)
EIP IP InstructionPointer
Segment selectors(16 bits)
CS CodeSegment
DS DataSegment
ES ExtraSegment
FS FSegment
GS GSegment
SS StackSegment
Status register
17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 (bit position)
V R 0 N IOPL O D I T S Z 0 A 0 P 1 C EFlags
Floating-point registers(80 bits)
79 ... 00 (bit position)
ST0 STack register 0
ST1 STack register 1
ST2 STack register 2
ST3 STack register 3
ST4 STack register 4
ST5 STack register 5
ST6 STack register 6
ST7 STack register 7

Theinstruction setof the i486 is very similar to the i386, with the addition of a few extra instructions, such as CMPXCHG, acompare-and-swapatomic operation,and XADD, afetch-and-addatomic operation that returned the original value (unlike a standard ADD, which returns flags only). This generation CPU has brought up to 156 different instructions listing.[14]

The i486's performance architecture is a vast improvement over the i386. It has an on-chip unified instruction and datacache,an on-chipfloating-point unit(FPU) and an enhancedbusinterface unit.[15]Due to the tight pipelining, sequences of simple instructions (such asALU reg,regandALU reg,im) could sustain single-clock-cycle throughput (one instruction completed every clock). In other words, it was running about 1.8 clocks per instruction.[6]These improvements yielded a rough doubling in integerALUperformance over the i386 at the sameclock rate.A 16 MHz i486 therefore had performance similar to a 33 MHz i386. With the combination both CPU and NPU house in the die would have bus utilization rate of 50% for the 25 MHz Intel486 version.[16]In other words, with the combination of both CPU and MCP (math coprocessor) provides 40% more performance than with both Intel386 DX and Intel387 DX math coprocessor combined.[17]The older design had to reach 50 MHz to be comparable with a 25 MHz i486 part.[d]

Differences between i386 and i486

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  • An 8KBon-chip (level 1)SRAMcachestores the most recently used instructions and data (16 KB and/orwrite-backon some later models). Thei386had no internal cache but supported a slower off-chip cache (not officially alevel 2 cachebecause 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[b]pipeliningcompletes a simple instruction like ALUreg,regor ALUreg,imevery clock cycle (after a latency of several cycles). The i386 needed two clock cycles.
  • IntegratedFPU(disabled or absent inSX models) with a dedicatedlocal bus;together with faster algorithms on more extensive hardware than in the i387, this performed floating-point calculations faster than thei386/i387combination.
  • ImprovedMMUperformance.
  • 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 inprotected mode,or to zero inreal mode,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 (realmode had novirtualaddresses). Just as with the i386, circumventing memory segmentation could substantially improve performance for someoperating systemsand applications.

On a typical PCmotherboard,either four matched 30-pin (8-bit)SIMMsor one 72-pin (32-bit) SIMM per bank were required to fit the i486's32-bitdata bus.Theaddress busused 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 4gigabytesas well (23032-bitwords = 2328-bitwords).

Models

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Intel offered several suffixes and variants (see table). Variants include:

  • Intel RapidCAD:a specially packaged Intel 486DX and a dummyfloating-point unit(FPU) designed as pin-compatible replacements for ani386processor and80387FPU.
  • i486SL-NM:i486SL based on i486SX.
  • i487SX (P23N):i486DX with one extra pin sold as an FPU upgrade toi486SXsystems; When the i487SX was installed, it ensured that an i486SX was present on themotherboardbut 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 byDell 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-micrometerfabrication 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 ofEISAsystems. The 486DX-50 was soon eclipsed by the clock-doubledi486DX2,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 andDX4were less popular (the latter available as an OEM part only), as they came out after Intel had released thenext-generation Pentiumprocessor family. Certain steppings of the DX4 also officially supported 50 MHz bus operation, but it was a seldom-used feature.

Model CPU/bus
clock speed		 Voltage L1 cache[e] Introduced Notes
i486DX (P4) 20, 25 MHz
33 MHz
50 MHz		 5 V 8 KB WT April 1989
May 1990
June 1991		 The original chip without clock multiplier
i486SL 20, 25, 33 MHz 5 V or 3.3 V 8 KB WT November 1992 Low-power version of the i486DX, reduced VCore, SMM (System Management Mode), stop clock, and power-saving features — mainly for use in portable computers
i486SX (P23) 16, 20, 25 MHz
33 MHz		 5 V 8 KB WT September 1991
September 1992		 An i486DX with the FPU part disabled; later versions had the FPU removed from thedieto reduce area and hence cost.
i486DX2 (P24) 40/20, 50/25 MHz
66/33 MHz		 5 V 8 KB WT March 1992
August 1992		 The internal processor clock runs at twice theclock rateof the external bus clock
i486DX-S (P4S) 33 MHz; 50 MHz 5 V or 3.3 V 8 KB WT June 1993 SL Enhanced 486DX
i486DX2-S (P24S) 40/20 MHz,
50/25 MHz,
(66/33 MHz)		 5 V or 3.3 V 8 KB WT June 1993 SL Enhanced 486DX2
i486SX-S (P23S) 25, 33 MHz 5 V or 3.3 V 8 KB WT June 1993 SL Enhanced 486SX
i486SX2 50/25, 66/33 MHz 5 V 8 KB WT March 1994 i486DX2 with the FPU disabled. Early version used the 800 nm process technology.[18]
IntelDX4 (P24C) 75/25, 100/33 MHz 3.3 V 16 KB WT March 1994 Designed to run at triple clock rate (not quadruple, as often believed; the DX3, which was meant to run at 2.5× the clock speed, was never released). DX4 models that featured write-back cache were identified by an "&EW" laser-etched into their top surface, while the write-through models were identified by "&E".
i486DX2WB (P24D) 50/25 MHz,
66/33 MHz		 5 V 8 KB WB October 1994 Enabled write-back cache.
IntelDX4WB 100/33 MHz 3.3 V 16 KB WB October 1994
i486DX2 (P24LM) 90/30 MHz,
100/33 MHz		 2.5–2.9 V 8 KB WT 1994
i486GX up to 33 MHz 3.3 V 8 KB WT Embedded ultra-low-power CPU with all features of the i486SX and 16-bit external data bus. This CPU is for embedded battery-operated and hand-held applications.

Other makers of 486-like CPUs

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STMicroelectronics' ST ST486DX2-40
UMC Green CPUU5SX
Cyrix Cx486DRx²

Processors compatible with the i486 were produced by companies such asIBM,Texas Instruments,AMD,Cyrix,UMC,andSTMicroelectronics(formerly SGS-Thomson). Some were clones (identical at the microarchitectural level), others wereclean room implementationsof 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.[19]

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, theAm5x86,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.

TheMotorola 68040,while not i486 compatible, was often positioned as its equivalent in features and performance. Clock-for-clock basis theMotorola 68040could significantly outperform the Intel chip.[20][21]However, the i486 had the ability to be clocked significantly faster without overheating.Motorola 68040performance lagged behind the later production i486 systems.[citation needed]

Motherboards and buses

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Thefirst 486 system from the UKon the cover of BYTE, September 1989

Early i486-based computers were equipped with severalISAslots (using anemulatedPC/AT-bus) and sometimes one or two8-bit-only slots (compatible with the PC/XT-bus).[f]Manymotherboardsenabled 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 theBIOSsetup. Especially older peripheral cards normally worked well at such speeds as they often used standard MSI chips instead of slower (at the time) customVLSIdesigns. 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 withSCSIorsound cards.

Some motherboards came equipped with a32-bitEISA 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, fasterVESA Local Bus(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 byPCIduring the final years of the i486 period. FewPentium classmotherboards 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, although ISA persisted well into the Pentium 4 era, especially among industrial PCs.

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 forVideo 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 manufacturerApricot Computers.[22]Even overseas in the United States it was popularized as "The World's First 486".

Later i486 boards supportedPlug-And-Play,a specification designed byMicrosoftthat began as a part ofWindows 95to make component installation easier for consumers.

Obsolescence

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TheAMD Am5x86andCyrix Cx5x86were the last i486 processors often used in late-generation i486 motherboards. They came with PCI slots and 72-pin SIMMs that were designed to runWindows 95,and also used for 80486 motherboards upgrades. While theCyrix Cx5x86faded when theCyrix 6x86took over, theAMD Am5x86remained important givenAMD K5delays.

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 theCeleronbrand, though it continued to be produced forembedded systemsthrough the late 2000s.

In the general-purpose desktop computer role, i486-based machines remained in use into the early 2000s, especially as Windows 95 through98andWindows NT 4.0were the last Microsoft operating systems to officially support i486-based systems.[23][24]Windows 2000could run on a i486-based machine, although with a less than optimal performance, due to the minimum hardware requirement of a Pentium processor.[25]However, as they were overtaken by newer operating systems, i486 systems fell out of use except forbackward compatibilitywith older programs (most notably games), especially given problems running on newer operating systems. However,DOSBoxwas available for later operating systems and provides emulation of the i486 instruction set, as well as full compatibility with most DOS-based programs.[26]

The i486 was eventually overtaken by the Pentium forpersonal computerapplications, although Intel continued production for use inembedded systems.In May 2006, Intel announced that production of the i486 would stop at the end of September 2007.[1][27]

See also

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  • List of Intel microprocessors
  • Motorola 68040,although not compatible, was often positioned as theMotorolaequivalent to the Intel 486 in terms of performance and features.
  • VL86C020,ARM3core of similar time frame and comparable MIPS performance on integer code (25 MHz for both), with 310,000 transistors (in a 1.5 μm process) instead of 1 million

Notes

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  1. ^AMD versions up to120and160MHz.
  2. ^abThe 386, 286, and even the 8086 all had overlapping fetch, decode, execution (calculation), and write back; however,tightly pipelinedusually means that all stages perform their respective duties within the same length time slot. In contrastloosely pipelinedimplies that some kind of buffering is used to decouple the units and allow them to work more independently. Both the original 8086 and the x86-chips of today are "loosely pipelined" in this sense, while the i486 and the original Pentium worked in a "tightly pipelined" manner for typical instructions. This included most "CISC"type instructions as well as the simple load/store-free"RISC-like "ones, although the most complex also used some dedicatedmicrocodecontrol.
  3. ^Simple instructions spend only a single clock cycle at each pipeline stage.[b]
  4. ^The pre-DX2 i486 parts did not use a clock multiplier and are therefore comparable to a twice-higher clocked 386/286.
  5. ^WT= write-through cache strategy,WB= write-back cache strategy.
  6. ^In general, 8-bit ISA slots in these systems were implemented just by leaving off the shorter "C" / "D" connector of the slot, though the copper traces for a 16-bit slot were still there on the motherboard; the computer could tell no difference between an 8-bit ISA adapter in such a slot and the same adapter in a 16-bit slot, and there were still enough 8-bit adapters in circulation that vendors figured they could save money on a few connectors this way. Also, leaving off the 16-bit extension to the ISA connector allowed use of some early 8-bit ISA cards that otherwise could not be used due to the PCB "skirt" hanging down into that 16-bit extension space. IBM was the first to do this in the IBM AT.

Further reading

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  • Gamer, Brassic (January 1, 2023)."The Brassic Gamer: The (Almost) Definitive 486DX/50 Article".The Brassic Gamer.RetrievedJanuary 3,2023.

References

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  1. ^abcd"Product Change Notification"(PDF).Intel. May 2, 2006. p. 2. Archived fromthe original(PDF)on October 9, 2006.
  2. ^abcdLewnes, Ann, "The Intel386 Architecture Here to Stay", Intel Corporation, Microcomputer Solutions, July/August 1989, page 2.
  3. ^abcIntel (July 1997).Embedded Intel486 Processor Hardware Reference Manual (273025-001).
  4. ^Chen, Allan, "The 50-MHz Intel486 Microprocessor", Intel Corporation, Microcomputer Solutions, September/October 1991, page 2.
  5. ^LotusChain (January 28, 2024)."FPU in CPU".LotusChain Medium.RetrievedSeptember 15,2024.
  6. ^abChen, Allan, "Designing A Mainframe on a Chip: Interview with the i486 Microprocessor Design Team", Intel Corporation, Microcomputer Solutions, July/August 1989, page 12.
  7. ^48632-bitCPU breaks new ground in chip density and operating performance. (Intel Corp.) (product announcement) EDN, May 11, 1989, Pryce, Dave.
  8. ^Lewis, Peter H. (October 22, 1989)."The Executive Computer; The Race to Market a 486 Machine".The New York Times.RetrievedMay 5,2010.
  9. ^Chen, Allan, "The 50-MHz Intel486 Microprocessor", Intel Corporation, Microcomputer Solutions, September/October 1991, page 2.
  10. ^Intel Corporation, "New Product Focus: Components: Modified Chips Cuts Portable Power Consumption", Microcomputer Solutions, November/December 1991, page 10.
  11. ^abcdefghijklmnopYates, Darren (November 2020). "Four. Eight. Six".APC.No. 486. Future Publishing. pp. 52–55.ISSN0725-4415.
  12. ^abcdLilly, Paul (April 14, 2009)."A Brief History of CPUs: 31 Awesome Years of x86".PC Gamer.RetrievedAugust 7,2021.
  13. ^Chauvet, Berenice D. (July 15, 1996)."School buys outdated computer model".Sun Sentinel.Tribune Publishing. Archived fromthe originalon July 2, 2021.
  14. ^House, Dave, "Putting the RISC vs. CISC Debate to Rest", Intel Corporation, Microcomputer Solutions, November/December 1991, page 18
  15. ^This article is based on material taken fromi486at theFree On-line Dictionary of Computingprior to 1 November 2008 and incorporated under the "relicensing" terms of theGFDL,version 1.3 or later.
  16. ^Intel Corporation, "Coming Attractions: Clock-Doubling Technology", Microcomputer Solutions, January/February 1992, page 6
  17. ^Intel Corporation, "A Guide to the Intel Architecture", Microcomputer Solutions, January/February 1992, page 11
  18. ^Intel Corporation, "Coming Attractions: Clock-Doubling Technology", Microcomputer Solutions, January/February 1992, page 6.
  19. ^"AMD-Intel Litigation History".yannalaw.com.
  20. ^"CISC: The Intel 80486 vs. The Motorola MC68040".July 1992.RetrievedMay 20,2013.
  21. ^68040 MicroprocessorArchivedFebruary 16, 2012, at theWayback Machine
  22. ^Lavin, Paul; Nadeau, Michael E. (September 1989)."The 486s Are Here".Byte.pp. 95–98.RetrievedApril 30,2022.
  23. ^"Minimum Hardware Requirements for a Windows 98 Installation".January 24, 2001. Archived fromthe originalon December 5, 2004.
  24. ^"Windows NT 4.0 Workstation"(in German). WinHistory.de.
  25. ^"World Record*: Windows 2000 running on Intel i486 SX 25 MHz".YouTube.July 29, 2013.
  26. ^"System Requirements".DOSBox.com.
  27. ^Tony Smith (May 18, 2006)."Intel cashes in ancient chips. i386, i486, i960 finally for the chop".The RegisterHardware. Archived fromthe originalon August 13, 2011.RetrievedMay 20,2012.
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