Am5x86

The Am5x86 (also known as the 5x86-133, Am5x86, X5-133, and sold under various 3rd-party labels such as the Kingston Technology "Turbochip"{{Cite news |date=5 June 1995 |title=Triple Your PC's Speed For Only $295 |pages=96 |work=InfoWorld |publisher=InfoWorld Media Group, Inc., Kingston Technology |url=https://books.google.com/books?id=wjoEAAAAMBAJ&dq=kingston+turbochip&pg=PT1 |access-date=10 March 2022 |issn=0199-6649}}) is an Enhanced Am486 processor with an internally set multiplier of 4, allowing it to run at 133 MHz on systems without official support for clock-multiplied DX2 or DX4 486 processors. Like all Enhanced Am486, the Am5x86 featured write-back L1 cache, and unlike all but a few, a generous 16 kilobytes rather than the more common 8 KB. A rare 150 MHz-rated OEM part was also released by AMD.

Since having a clock multiplier of four is not part of the original Socket 3 design (and that the 486 only have a single CLKMUL pin anyway), AMD made the 5x86 accept a 2x setting from the motherboard and instead operate at a rate of 4x.{{Cite book |last=Mueller |first=Scott |url=https://books.google.com/books?id=eV1_LjW3pTkC |title=Upgrading and Repairing PCs |publisher=Que |year=2003 |isbn=9780789727459 |pages=133}} When using an Am5x86, the motherboard must be set to the 2x setting. The chip will actually physically fit into an older 486 socket such as a socket 1 or 2 or the original 168-pin 80486 socket, but doing this requires a replacement voltage regulator, since the AMD chip runs at 3.45 volts.

The combination of clock speed and the relatively large 16 KB write-back L1 cache allows the 5x86 to equal or slightly exceed an Intel Pentium 75 MHz processor in integer arithmetic in benchmarks.{{Cite book |url=https://books.google.com/books?id=dpFQAAAAMAAJ&q=amd+5x86 |title=Conference Proceedings |publisher=Association for Computing Machinery |year=1999 |volume=27 |pages=95|isbn=9781581131444 }} Real world performance varies, however, with later Windows operating systems and many FPU-sensitive games favoring the Pentium 75 MHz. Because it is based on a pure 486 design, it is compatible with older systems, something its slightly faster rival, the Cyrix Cx5x86, has trouble with. The CPU is commonly overclocked to 160 MHz, thereby giving performance similar to that of a Pentium 90 MHz system. There are four main versions of the socketed version of this CPU, manufactured in different locations. There is the common ADW variety, as well as the later ADY, ADZ and BGC. The later models were the preferred versions of the chip, because they were rated for higher temperatures and thus more forgiving of overclocking.

The Am5x86 made the first-ever use of the controversial PR rating.{{Cite web|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-x86/3/|url-status=live|access-date=2021-08-07|website=PC Gamer|language=en|df=mdy|archive-url=https://web.archive.org/web/20160411130111/http://www.pcgamer.com:80/a-brief-history-of-cpus-31-awesome-years-of-x86/3/ |archive-date=2016-04-11 }} Because the 5x86 is the equal of a Pentium 75 MHz processor in benchmarks, AMD later marketed the chip as "Am5x86-P75".{{Cite news |date=August 1996 |title=What the Numbers Mean |volume=15 |pages=132 |work=PC Mag |issue=14 |publisher=Ziff Davis, Inc. |url=https://books.google.com/books?id=ZV8jJvJv-zYC&dq=Am5x86-P75&pg=PA132 |access-date=10 March 2022 |issn=0888-8507}}

Sales of the Am5x86 were an important source of revenue for AMD at a time when lengthy delays in bringing the AMD K5 to production were threatening the company's profitability.{{Cite news |year=1995 |title=AMD's K5 Delayed |pages=19 |work=Dataquest: DQ |url=https://books.google.com/books?id=61kTAQAAMAAJ&q=amd+k5+delay |access-date=10 March 2022}}{{Cite news |date=2 October 1995 |title=AMD's K5 Faces Another Delay |pages=20 |work=InfoWorld |publisher=InfoWorld Media Group, Inc. |url=https://books.google.com/books?id=XDoEAAAAMBAJ&dq=amd+k5+delay&pg=PA20 |access-date=10 March 2022 |issn=0199-6649}}

AMD manufactured the Am5x86 processor for ordinary PC systems until 1999. It was popular for entry-level desktop systems, appeared in many different notebook models, and also sold separately as an upgrade processor for older 486 systems. Several companies made upgrade kits with an AMD 5x86 with a voltage regulator and socket converter, which allows its use on virtually every socketed 486 motherboard ever produced. Several companies also provided upgrades for older 486 notebooks by replacing soldered 486 CPUs. The chips were even used on later Acorn RiscPC "PC card" second processors. The RiscPC's OpenBus memory interface was only 32 bit, which meant that the Pentium could not be easily interfaced to it. Intel's expensive Pentium Overdrive for 486 systems is a troublesome CPU, with many compatibility issues, and so is not used. The 5x86 therefore provided the acme of RiscPC Windows performance.

The chip remained in production for a long time, as it was a popular choice for use in embedded controllers. One derivative of the 5x86 family is the core used in the AMD Élan SC520 family of SoC 00200microcontrollers marketed by AMD.{{Cite book |url=https://www.amd.com/system/files/TechDocs/22004b.pdf |title=Élan™SC520 Microcontroller User's Manual |publisher=AMD |pages=23}} This powers the original Cisco PIX 501 model.{{Cite book |last=Newman |first=Daniel |url=https://www.pearsonitcertification.com/articles/article.aspx?p=101741&seqNum=6 |title=CCSP CSPFA Exam Cram 2 (Exam Cram 642-521) |publisher=Pearson IT Certification |year=2003 |pages=6 |chapter=Basics of the PIX Firewall}}

AMD Am5x86-P75 (cropped).jpg|An Am5x86-P75 model ADZ

Ic-photo-AMD--Am5x86-P75-(Am486DX5-133W16BGC)-(486-CPU).jpg|A late Am5x86-P75 for Socket 3, model W16BGC

Kl AMD Am5x86-P75 PQFP.jpg|Surface-mounted Am5x86-P75, model V16BHC

AMD Am5x86 die.JPG|AMD Am5x86 die shot

AMD Elan SC520-133AC.jpg|AMD Élan SC520 system on a chip based on the Am5x86 core

Data from{{cite web |last=Shvets |first=Gennadiy |url=http://www.cpu-world.com/CPUs/80486/MANUF-AMD.html |title=AMD 80486 microprocessor |work=CPU-World |date=25 July 2016 |access-date=25 July 2016}}{{cite web |title=The AMD 5x86 Processor |url=http://www.cpu-collection.de/?l0=co&l1=AMD&l2=5x86#Am5x86-P75+X5-150ADW |work=cpu-collection.de |year=2011 |access-date=14 November 2011}}{{Cite web|url=http://www.cpu-galerie.de/html/amd5x86.html#160ADZ|title = AMD 5x86 CPU Sammlung | cpu-galerie.de}}

{{Commons category|AMD Am5x86}}

• [https://web.archive.org/web/20020205215236/http://www.amd.com/us-en/Processors/ProductInformation/0%2C%2C30_118_1260_1268%2C00.html AMD: The Am5x86 Microprocessor (via archive.org: Feb 5, 2002)]
• [http://web.inter.nl.net/hcc/J.Steunebrink/amd5x86.htm CPU Upgrade: Give your 486 PC a kick with the AMD 5x86 - 133!] {{Webarchive|url=https://web.archive.org/web/20080306102623/http://web.inter.nl.net/hcc/J.Steunebrink/amd5x86.htm |date=2008-03-06 }}
• [http://www.cpushack.com/chippics/AMD/8048x/ Gallery including Am586 images] at [http://www.cpushack.com Cpushack.com]
• [https://web.archive.org/web/20040206205027/http://www.amd.com/epd/processors/4.32bitcont/14.lan5xxfam/24.lansc520/index.html AMD's Élan μController family (via archive.org: Feb 6, 2004)]
• [http://www.cpu-collection.de/?l0=co&l1=AMD&l2=5x86 AMD 5x86 processor images and descriptions at cpu-collection.de]

{{AMD_processors}}

Am586

Category:X86 microarchitectures

Category:Computer-related introductions in 1995