Editing I486 (section)

==History==
The concept of this microprocessor generation was discussed with [[Pat Gelsinger]] and [[John Crawford (engineer)|John Crawford]] shortly after the release of [[I386|386 processor]] in 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 the [[Tape-out|tape out]] on March 1.  They received the first silicon from the fabrication on March 20.<ref name="Chen, Allan 1989, page 12">Chen, Allan, "Designing A Mainframe on a Chip: Interview with the i486 Microprocessor Design Team", Intel Corporation, Microcomputer Solutions, July/August 1989, page 12.</ref>

The i486 was announced at Spring [[COMDEX|Comdex]] in April 10, 1989.<ref name="Lewnes, Ann 1989, page 2">Lewnes, Ann, "The Intel386 Architecture Here to Stay", Intel Corporation, Microcomputer Solutions, July/August 1989, page 2.</ref> At the announcement, Intel stated that samples would be available in the third quarter and production quantities would ship in the fourth quarter.<ref>486 [[32-bit computing|32-bit]] CPU breaks new ground in chip density and operating performance. (Intel Corp.) (product announcement) EDN, May 11, 1989, Pryce, Dave.</ref> The first i486-based PCs were announced in late 1989.<ref>{{cite news |url = https://www.nytimes.com/1989/10/22/business/the-executive-computer-the-race-to-market-a-486-machine.html?pagewanted=1 |work = The New York Times |title = The Executive Computer; The Race to Market a 486 Machine |first = Peter H. |last = Lewis |date = October 22, 1989 |access-date = May 5, 2010 }}</ref>

In fall of 1991, Intel introduced the 50 MHz i486&nbsp;DX using the three layer [[800&nbsp;nm process]] [[CHMOS|CHMOS-V]] technology. They were available for US$665 in 1,000-unit quantities.<ref>Chen, Allan, "The 50-MHz Intel486 Microprocessor", Intel Corporation, Microcomputer Solutions, September/October 1991, page 2.</ref>

In that season, Intel introduced low-power 25 MHz Intel486&nbsp;DX microprocessor. This one was available for US$471. Also, there were low-power 16, 20, and 25&nbsp;MHz Intel486&nbsp;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.<ref>Intel Corporation, "New Product Focus: Components: Modified Chips Cuts Portable Power Consumption", Microcomputer Solutions, November/December 1991, page 10.</ref>

The first major update to the i486 design came in March 1992 with the release of the clock-doubled [[Intel DX2|486DX2]] series.<ref name=":0">{{Cite magazine |last=Yates |first=Darren |date=November 2020 |title=Four. Eight. Six. |magazine=[[APC (magazine)|APC]] |language=en |publisher=Future Publishing |issue=486 |pages=52–55 |issn=0725-4415}}</ref> It was the first time that the CPU core clock frequency was separated from the [[system bus]] clock frequency by using a dual clock multiplier, supporting 486DX2 chips at 40 and 50&nbsp;MHz. The faster 66&nbsp;MHz 486DX2-66 was released that August.<ref name=":0" />

The fifth-generation [[Pentium (original)|Pentium]] processor launched in 1993, while Intel continued to produce i486 processors, including the triple-clock-rate [[Intel DX4|486DX4-100]] with a 100&nbsp;MHz clock speed and a L1 cache doubled to 16&nbsp;KB.<ref name=":0" />

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.<ref name=":0" /> AMD reverse-engineered the 386 and produced the 40&nbsp;MHz [[Am386|Am386DX-40]] chip, which was cheaper and had lower power consumption than Intel's best 33&nbsp;MHz version.<ref name=":0" /> Intel attempted to prevent AMD from selling the processor, but AMD won in court, which allowed it to establish itself as a competitor.<ref name=":1">{{Cite web <!--Deny Citation Bot--> |last=Lilly |first=Paul |date=2009-04-14 |title=A Brief History of CPUs: 31 Awesome Years of x86 |url=https://www.pcgamer.com/a-brief-history-of-cpus-31-awesome-years-of-x86/ |access-date=2021-08-07 |website=PC Gamer |language=en}}</ref>

AMD continued to create clones, releasing the first-generation [[Am486]] chip in April 1993 with clock frequencies of 25, 33 and 40&nbsp;MHz. Second-generation Am486DX2 chips with 50, 66 and 80&nbsp;MHz clock frequencies were released the following year.<ref name=":0" /> The Am486 series was completed with a 120&nbsp;MHz DX4 chip in 1995.<ref name=":0" />

AMD's long-running 1987 arbitration lawsuit against Intel was settled in 1995, and AMD gained access to Intel's 80486 microcode.<ref name=":0" /> This led to the creation of two versions of AMD's 486 processor{{snd}} one reverse-engineered from Intel's microcode, while the other used AMD's microcode in a [[clean-room design]] process. However, the settlement also concluded that the 80486 would be AMD's last Intel clone.<ref name=":0" />

Another 486 clone manufacturer was [[Cyrix]], which was a [[Fabless manufacturing|fabless]] co-processor chip maker for 80286/386 systems. The first [[Cyrix Cx486|Cyrix 486]] processors, the 486SLC and 486DLC, were released in 1992 and used the 80386 package.<ref name=":0" /> Both [[Texas Instruments]]-manufactured Cyrix processors were pin-compatible with 386SX/DX systems, which allowed them to become an upgrade option.<ref name=":1" /> However, these chips could not match the Intel 486 processors, having only 1&nbsp;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 for [[patent infringement]], and Cyrix for [[antitrust]] claims. In 1994, Cyrix won the patent infringement case and dropped its antitrust claim.<ref name=":0" />

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 [[Cyrix 5x86|5x86]], based on the Cyrix M1 core, which was clocked up to 120&nbsp;MHz and was an option for 486 Socket&nbsp;3 motherboards.<ref name=":0" /><ref name=":1" /> AMD released a 133&nbsp;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.<ref name=":0" /> 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&nbsp;75.<ref name=":1" /> [[Kingston Technology]] launched a "TurboChip" 486 system upgrade that used a 133&nbsp;MHz Am5x86.<ref name=":0" />

Intel responded by making a [[Pentium OverDrive]] upgrade chip for 486 motherboards, which was a modified Pentium core that ran up to 83&nbsp;MHz on boards with a 25 or 33&nbsp;MHz front-side bus clock. OverDrive wasn't popular due to speed and price.<ref name=":0" /> New computers equipped with 486 processors in discount warehouses became scarce, and an [[IBM]] spokesperson called it a "dinosaur".<ref name="chauvet-1996">{{cite news |first=Berenice D. |last=Chauvet |work=Sun Sentinel |title=School buys outdated computer model |url=https://www.sun-sentinel.com/news/fl-xpm-1996-07-15-9607140215-story.html |archiveurl=https://web.archive.org/web/20210702154637/https://www.sun-sentinel.com/news/fl-xpm-1996-07-15-9607140215-story.html |archivedate=July 2, 2021 |date=July 15, 1996 |publisher=Tribune Publishing}}</ref> 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.<ref name="i486LastShipment2007"/><ref name=":0" />