Editing I486 (section)

==Other makers of 486-like CPUs==
[[File:KL STMicroelectronics ST486DX2-40.jpg|thumb|150px|STMicroelectronics' ST ST486DX2-40]]
[[File:KL UMC U5SX.jpg|thumb|150px|[[UMC Green CPU]] U5SX]]
[[Image:KL Cyrix 486DRx2.jpg|thumb|right|150px|Cyrix Cx486DRx²]]
Processors compatible with the i486 were produced by companies such as [[IBM]], [[Texas Instruments]], [[AMD]], [[Cyrix]], [[United Microelectronics Corporation|UMC]], and [[STMicroelectronics]] (formerly SGS-Thomson). Some were clones (identical at the microarchitectural level), others were [[clean room design|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.<ref>{{cite web|title=AMD-Intel Litigation History|url=https://yannalaw.com/services/trials-litigation/litigation-cottage-industry/amd-intel-litigation/|website=yannalaw.com}}</ref>

AMD produced several clones using a 40&nbsp;MHz bus (486DX-40, 486DX/2-80, and 486DX/4-120) which had no Intel equivalent, as well as a part specified for 90&nbsp;MHz, using a 30&nbsp;MHz external clock, that was sold only to OEMs. The fastest running i486-compatible CPU, the [[Am5x86]], ran at 133&nbsp;MHz and was released by AMD in 1995. 150&nbsp;MHz and 160&nbsp;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 [[Cyrix_Cx486DLC|486DLC]] and 486SLC, two hybrid chips that plugged into 386DX or SX sockets respectively, and offered 1&nbsp;KB of cache (versus 8&nbsp;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&nbsp;KB of cache. Clock-for-clock, the Cyrix-made chips were generally slower than their Intel/AMD equivalents, though later products with 8&nbsp;KB caches were more competitive, albeit late to market.

The [[Motorola 68040]], while not i486 compatible, was often positioned as its equivalent in features and performance. Clock-for-clock basis the [[Motorola 68040]] could significantly outperform the Intel chip.<ref>{{cite web|title=CISC: The Intel 80486 vs. The Motorola MC68040|url=http://textfiles.meulie.net/computers/486vs040.txt|access-date=May 20, 2013|date=July 1992}}</ref><ref>[http://www.bbs.ingedigit.com.ve/TechInfo/68040.Microprocessor.html 68040 Microprocessor] {{webarchive |url=https://web.archive.org/web/20120216013510/http://www.bbs.ingedigit.com.ve/TechInfo/68040.Microprocessor.html |date=February 16, 2012 }}</ref> However, the i486 had the ability to be clocked significantly faster without overheating. [[Motorola 68040]] performance lagged behind the later production i486 systems.{{Citation needed|date=July 2015}}