{{Short description|AMD microprocessor clone}} {{Infobox CPU |name = Am386 |image = Am386DX-40.jpg |image_size = 200px |caption = An AMD 80386DX-40 in a 132-pin PQFP, soldered onboard |produced-start = 1991 |produced-end = |slowest = 20 |slow-unit = MHz |fastest = 40 |fast-unit = MHz |fsb-slowest = 20 |fsb-slow-unit = MHz |fsb-fastest = 40 |fsb-fast-unit = MHz |size-from = 1.5 μm |size-to = 0.8 μm |soldby = AMD |designfirm = AMD |manuf1 = AMD |pack1 = '''DX variant''':<br /> 132-pin PGA |pack2 = 132-pin PQFP |pack3 = '''SX variant''':<br /> 88-pin PGA |pack4 = 100-pin PQFP |pack5 = '''DE variant''':<br /> 132-pin PGA<br /> 132-pin PQFP |brand1 = |arch = x86 (IA-32) |microarch = 80386 |cpuid = |code = 23936 |numcores = 1 |l1cache = Motherboard dependent |l2cache = none |application = Desktop, Embedded (DE/SE-Models) |predecessor = Am286 |successor = Am486 }}
The '''Am386''' CPU is a 100%-compatible clone of the Intel 80386 design released by AMD in March 1991. It sold millions of units, positioning AMD as a legitimate competitor to Intel, rather than being merely a second source for ''x86'' CPUs (then termed ''8086-family'').<ref name="cpu-collection">{{cite web |title=The AMD Am386 DX Processor |url=http://www.cpu-collection.de/?l0=co&l1=AMD&l2=386+DX |work=cpu-collection.de |year=2011 |access-date=12 November 2011}}</ref>
==History and design== thumb|Wafer of an Am386 processor with Intel copyright notice [[File:AMD_80386DX_die.JPG|right|thumb|Die of AMD Am386DX]] While the AM386 CPU was essentially ready to be released prior to 1991, Intel kept it tied up in court.<ref name="CPU-World">{{cite web |last=Shvets |first=Gennadiy |title=AMD 80386 microprocessor |url=http://www.cpu-world.com/CPUs/80386/MANUF-AMD.html |work=CPU-World |date=5 November 2011 |access-date=29 November 2011}}</ref> Intel learned of the Am386 when both companies hired employees with the same name who coincidentally stayed at the same hotel, which accidentally forwarded a package for AMD to Intel's employee.<ref name="LA Times">{{cite news |author=Jonathan Weber |title=AMD-Intel Battle Now Tangled in 2 'Webbs' |url=https://www.latimes.com/archives/la-xpm-1990-10-05-fi-1767-story.html |date=October 5, 1990 |access-date=December 26, 2024}}</ref> AMD had previously been a second-source manufacturer of Intel's Intel 8086, Intel 80186 and Intel 80286 designs, and AMD's interpretation of the contract, made up in 1982, was that it covered all derivatives of them. Intel, however, claimed that the contract only covered the 80286 and prior processors and forbade AMD the right to manufacture 80386 CPUs in 1987. After a few years in the courtrooms, AMD finally won the case and the right to sell their Am386 in March 1991.<ref>{{Cite news|url=https://www.nytimes.com/1991/03/02/business/intel-loses-trademark-decision.html|title=Intel Loses Trademark Decision|first1=Andrew|last1=Pollack|work=The New York Times |date=2 March 1991 }}</ref> This also paved the way for competition in the 80386-compatible 32-bit CPU market and so lowered the cost of owning a PC.<ref name="cpu-collection" />
While Intel's 386 CPUs had topped out at 33 MHz in 1989, AMD introduced 40 MHz versions of both its 386DX and 386SX out of the gate, extending the lifespan of the architecture. In the following two years the AMD 386DX-40 saw popularity with small manufacturers of PC clones and with budget-minded computer enthusiasts because it offered near-80486 performance at a much lower price than an actual 486.<ref>{{cite web |url=http://www.redhill.net.au/c/c-4.html |work=the red hill cpu guide |title=386DX-40 and competitors |year=2011 |access-date=12 November 2011}}</ref> Generally the 386DX-40 performs nearly on par with a 25 MHz 486 due to the 486 needing fewer clock cycles per instruction, thanks to its tighter pipelining (more overlapping of internal processing) in combination with an on-chip CPU cache. However, its 32-bit 40 MHz data bus gave the 386DX-40 comparatively good memory and I/O performance.<ref>{{cite web |last1=Linderholm |first1=Owen |last2=Miller |first2=Dan |title=486SX-25s vs. 386DX-40s: the upstart fights back. (evaluations of 30 microcomputers based on Intel Corp.'s 80486SX-25, 80386DX-40 microprocessors) (Hardware Review) (Systems: 486SX-25 vs. 386-40) (Evaluation) |url=http://business.highbeam.com/409748/article-1G1-13042739/486sx25s-vs-386dx40s-upstart-fights-back |archive-url=https://web.archive.org/web/20140101094653/http://business.highbeam.com/409748/article-1G1-13042739/486sx25s-vs-386dx40s-upstart-fights-back |url-status=dead |archive-date=1 January 2014 |date=1 December 1992 |access-date=12 November 2011}}</ref>
Intel responded to AMD's 40-Mhz 386 with the 486SX.<ref name="machrone19910924">{{Cite magazine |last=Machrone |first=Bill |date=1991-09-24 |title=Is There Life After 33 MHz? |url=https://books.google.com/books?id=6UNWdidjDmIC&pg=PP115 |access-date=March 1, 2026 |magazine=PC |pages=85-86 |volume=10 |issue=16}}</ref>
<gallery> File:KL AMD 386DX.jpg|An Am386DX-25 File:KL AMD Am386DE.jpg|The Am386DE-33 is an embedded version of the Am386DX-33. File:AMD Am386DX DXL.jpg|A PGA Am386DX-40 File:AMD Am386 DX-40 2007 03 27.jpg|A PQFP Am386DX-40 on a 132-pin PGA adapter File:AMD Am386DE Block Diagram.tif|AMD Am386DE block diagram. There is not a Paging Unit like a DX CPU. File:Early Nineties 386DX-40.png|A scan of an AMD Am386™DX-40 mounted on a PGA adapter </gallery>
===Am386DX data=== * 32-bit data bus, can select between either a 32-bit bus or a 16-bit bus by use of the BS16 input * 32-bit physical address space, 4 Gbyte physical memory address space * fetches code in four-byte units * released in March 1991 (October 1991 for DXLV/SXLV variants with SMM<ref name="wharton1994">John Wharton, [https://bitsavers.org/pdf/microDesign/Microdesign_-_The_Complete_X86_Volume_1_1994.pdf The Complete x86 - The Definitive Guide to 386, 486, and Pentium-Class Microprocessors Volume I], ''MicroDesign Resources'', see page 195 for Am386SXLV and page 200 for Am386DXLV.</ref>)
{| class="wikitable" |+ The various models of the Am386DX, data from<ref name="cpu-collection" /><ref name="CPU-World" /> ! Model number !! Frequency !! FSB !! Voltage !! Power !! Socket |- | AMD Am386DX/DXL-20 || colspan="2" | 20 MHz || rowspan="5" | 5 V || 1.05 Watt || rowspan="4" | 132-pin CPGA |- | AMD Am386DX/DXL-25 || colspan="2" | 25 MHz || 1.31 Watt |- | AMD Am386DX/DXL-33 || colspan="2" | 33 MHz || 1.73 Watt |- | AMD Am386DX/DXL-40 || colspan="2" rowspan="2" | 40 MHz || 2.10 Watt |- | AMD Am386DX-40 || 3.03 Watt || 132-pin PQFP |- | AMD Am386DXLV-25 || colspan="2" | 25 MHz || 3-5 V || 445 mW (at 3.3V) || rowspan="2" | 132-pin PQFP,<ref name="amd1992_386book">AMD, [http://www.bitsavers.org/components/amd/x86/1992_AMD_Personal_Computer_Microprocessors_Data_Book.pdf Personal Computer Microprocessors Data Book], 1992 - see pages 436-444 for information on Am386DXLV and pages 459-467 for information on Am386SXLV.</ref><br/>132-pin PGA<ref name="wharton1994"/> |- | AMD Am386DXLV-33 || colspan="2" | 33 MHz || 5 V || 1.65 Watt |}
===Am386DE data=== * 32-bit data bus, can select between either a 32-bit bus or a 16-bit bus by use of the BS16 input * 32-bit physical address space, 4 Gbyte physical memory address space * fetches code in four-byte units * no paging unit<ref name="mpr_386de">Microprocessor Report, [https://www.ardent-tool.com/CPU/docs/MPR/19940307/0803msb.pdf Vol.8, No.3, March 7, 1994, "Most Significant Bits"], pages 1-2</ref>
{| class="wikitable" |+ The various models of the Am386DE, data from<ref name="cpu-collection" /><ref name="CPU-World" /> ! Model number !! Frequency !! FSB !! Voltage !! Power !! Socket !! Release date |- | AMD Am386DE-25KC || colspan="2" | 25 MHz || 3-5 V || 0.32-1.05 Watt || rowspan="2" | 132-pin PQFP || rowspan="3" | 1994<ref name="mpr_386de"/> |- | AMD Am386DE-33KC || colspan="2" rowspan="2" | 33 MHz || rowspan="2" | 5 V || rowspan="2" | 1.05-1.35 Watt |- | AMD Am386DE-33GC || 132-pin CPGA |}
==AM386 SX== In 1991 AMD also introduced advanced versions of the 386SX processor – again not as a second source production of the Intel chip, but as a reverse engineered pin compatible version. In fact, it was AMD's first entry in the x86 market other than as a second source for Intel.<ref name="cpu-collection-SX">{{cite web |title=The AMD Am386 SX Processor |url=http://www.cpu-collection.de/?tn=0&l0=co&l1=AMD&l2=386+SX |work=cpu-collection.de |year=2011 |access-date=30 November 2011}}</ref> AMD 386SX processors were available at higher clock speeds at the time they were introduced and still cheaper than the Intel 386SX. Produced in 0.8 μm technology and using a static core, their clock speed could be dropped down to 0 MHz, consuming just some mWatts. Power consumption was up to 35% lower than with Intel's design and even lower than the 386SL's, making the AMD 386SX the ideal chip for both desktop and mobile computers. The SXL versions featured advanced power management functions and used even less power.<ref name="cpu-collection-SX" />
<gallery> File:Microspot DC-300 - board 2 --AMD Am386SX-SXL-25-8443.jpg|An Am386SX-25 File:KL AMD 386SX.jpg|An Am386SX-33 File:Ic-photo-AMD--Am386SX-40--(NG80386SX-40)--(386-CPU).png|An Am386SX-40 </gallery>
===Am386SX data=== * 16-bit data bus, no bus sizing option * 24-bit physical address space, 16 Mbyte physical memory address space * prefetch unit reads two bytes as one unit (like the 80286). {| class="wikitable" |+ The various models of the Am386SX, data from<ref name="CPU-World" /><ref name="cpu-collection-SX" /><ref name="AMD Am386 Microprocessors for Personal Computers Datasheet">[http://bitsavers.informatik.uni-stuttgart.de/pdf/amd/_dataBooks/1992_AM386_Microprocessors_for_Personal_Computers.pdf] {{Webarchive|url=https://web.archive.org/web/20160304200038/http://bitsavers.informatik.uni-stuttgart.de/pdf/amd/_dataBooks/1992_AM386_Microprocessors_for_Personal_Computers.pdf|date=2016-03-04}}, AMD Datasheet no 15022.</ref> ! Model number !! Frequency !! FSB !! Voltage !! Power !! Socket !! Release date |- | AMD Am386SX/SXL-20 || colspan="2" | 20 MHz || rowspan="4" | 5 V || 1.68/0.85 Watt || rowspan="4" | 100-pin PQFP || 1991 |- | AMD Am386SX/SXL-25 || colspan="2" | 25 MHz || 1.84/1.05 Watt || 29 April 1991 |- | AMD Am386SX/SXL-33 || colspan="2" | 33 MHz || 1.35 Watt || 1992 |- | AMD Am386SX-40 || colspan="2" | 40 MHz || 1.55 Watt || 1991 |- | AMD Am386SXLV-20 || colspan="2" | 20 MHz || rowspan="2" | 3-5V || || rowspan="2" | 100-pin PQFP<ref name="amd1992_386book"/> || rowspan="2" | October 1991<ref name="wharton1994"/> |- | AMD Am386SXLV-25 || colspan="2" | 25 MHz || 412 mW (at 3.3V)<ref name="wharton1994"/> |}
===Am386SE data=== * 16-bit data bus, no bus sizing option * 24-bit physical address space, 16 Mbyte physical memory address space * prefetch unit reads two bytes as one unit (like the 80286). * no paging unit<ref name="mpr_386de"/>
{| class="wikitable" |+ The various models of the Am386SE, data from<ref name="am386se_datasheet">AMD, [https://4donline.ihs.com/images/VipMasterIC/IC/AMDI/AMDIS045/AMDIS045-1.pdf?hkey=FB3F1F3F2A09A989A6BF9D772C3B8264 Am386SE High Performance, Low-Power, 32-bit Embedded Microprocessor], pub.no. 18420, rev B, June 1994, see page 7 for product list and pages 60-61 for DC characteristics. [https://web.archive.org/web/20250125151653/https://4donline.ihs.com/images/VipMasterIC/IC/AMDI/AMDIS045/AMDIS045-1.pdf?hkey=FB3F1F3F2A09A989A6BF9D772C3B8264 Archived] on 25 Jan 2025.</ref> ! Model number !! Frequency !! FSB !! Voltage !! Socket !! Release date |- | AMD Am386SE-25KC || colspan="2" rowspan="4" | 25 MHz || rowspan="4" | 3-5 V || rowspan="2" | 100-pin PQFP || rowspan="5" | 1994<ref name="mpr_386de" /> |- | AMD Am386SE-25KI |- | AMD Am386SE-25VC || rowspan="2" | 100-pin TQFP |- | AMD Am386SE-25VI |- | AMD Am386SE-33KC || colspan="2" | 33 MHz || 5 V || 100-pin PQFP |}
==Embedded Am386 processors== {{See also|AMD Élan}} The Am386 processor core has been used in some embedded processors. In October 1993, AMD introduced the Am386SC processor, which integrated an Am386SXLV CPU core with a collection of PC/AT-compatible peripherals.<ref>Microprocessor Report, [https://www.ardent-tool.com/CPU/docs/MPR/19931025/071404.pdf AMD’s Elan Puts 386 PC in Pocket] (vol 7, no. 14, October 25, 1993). [https://web.archive.org/web/20240422074042/https://www.ardent-tool.com/CPU/docs/MPR/19931025/071404.pdf Archived] on 22 Apr 2024.</ref> This processor, marketed as "Élan SC300" and "Élan SC310", was the first in AMD's Élan series of SoCs. In 1994, AMD announced the Am386EM microcontroller, which integrated an Am386 CPU core with a collection of 80186-compatible peripherals rather than PC/AT peripherals.<ref>Microprocessor Report, [https://www.ardent-tool.com/CPU/docs/MPR/19941003/0813msb.pdf Most Significant bits] (vol 8, No. 13, October 3, 1994), page 3. [https://web.archive.org/web/20240422074119/https://www.ardent-tool.com/CPU/docs/MPR/19941003/0813msb.pdf Archived] on 22 Apr 2024.</ref><ref>Tech Monitor, [https://www.techmonitor.ai/technology/advanced_micro_creates_iapx_86_microcontrollers?cf-view Advanced Micro Creates iAPX-86 Microcontrollers], 26 Sep 1994. [https://web.archive.org/web/20250126202613/https://www.techmonitor.ai/technology/advanced_micro_creates_iapx_86_microcontrollers?cf-view Archived] on 26 Jan 2025.</ref> This chip does not, however, appear to have been released,<ref>R. Oestergaard, [https://groups.google.com/g/comp.arch.embedded/c/JAzuW5AWnGo/m/K0eACgbyWWsJ What comes after 80186?], 14 dec 1995, ''comp.arch.embedded'' newsgroup post. [https://web.archive.org/web/20250126203447/https://groups.google.com/g/comp.arch.embedded/c/JAzuW5AWnGo/m/K0eACgbyWWsJ Archived] on 26 Jan 2025.</ref> although a datasheet exists.<ref>AMD, [https://4donline.ihs.com/images/VipMasterIC/IC/AMDI/AMDIS014/AMDIS014-1.pdf?hkey=FB3F1F3F2A09A989A6BF9D772C3B8264 Am386EM 386-Based 80C186/8-Compatible 32-bit Embedded Microcontroller], pub.no. 19167, rev A, august 1994. [https://web.archive.org/web/20250624181037/https://4donline.ihs.com/images/VipMasterIC/IC/AMDI/AMDIS014/AMDIS014-1.pdf?hkey=FB3F1F3F2A09A989A6BF9D772C3B8264 Archived] on 24 Jun 2025.</ref>
==i387 coprocessor== Floating point performance of the Am386 could be boosted with the addition of a i387DX or i387SX coprocessor, although performance would still not approach that of the on-chip FPU of the i486DX. This made the Am386DX a suboptimal choice for scientific applications and CAD using floating point intensive calculations. However, both were niche markets in the early 1990s and the chip sold well, first as a mid-range contender, and then as a budget chip. Although motherboards using the older 386 CPUs often had limited memory expansion possibilities and therefore struggled under Windows 95's memory requirements, boards using the Am386 were sold well into the mid-1990s; at the end as budget motherboards for those who were only interested in running MS-DOS or Windows 3.1x applications. The Am386 and its low-power successors were also popular choices for embedded systems, for a much longer period than their life span as PC processors.
<gallery> File:KL IIT 3C87SX.jpg|An IIT 387SX-25 Coprocessor File:FasMath.jpg|A Cyrix FasMath 387DX-33 Coprocessor File:KL ULSI US83S87SX SLC.jpg|An ULSI 387SX-40 Coprocessor </gallery>
==References== {{Reflist}}
==External links== {{Commons category}} * [https://www.amd.com/epd/processors/6.32bitproc/10.am386fami/ AMD.com: Am386 Family 32-bit Processors] * [http://support.amd.com/us/Embedded_TechDocs/21020.pdf AMD Am386SX/SXL/SXLV Datasheet] * [http://www.cpu-collection.de/?l0=co&l1=AMD&l2=386%20DX cpu-collection.de: Pictures] * [http://www.digital-daily.com/editorial/amd-history/index02.htm AMD: 30 Years of Pursuing the Leader. Part 2] * {{cite web |last=Shvets |first=Gennadiy |title=AMD 80386 microprocessor |url=http://www.cpu-world.com/CPUs/80386/MANUF-AMD.html |work=CPU-World |date=5 November 2011 |access-date=29 November 2011}} * [http://bitsavers.informatik.uni-stuttgart.de/components/amd/_dataBooks/1992_AM386_Microprocessors_for_Personal_Computers.pdf AMD Am386 Microprocessors for Personal Computers Datasheet 15021 and 15022] * {{usurped|1=[https://web.archive.org/web/20160819054824/http://www.datasheetlib.com/datasheet/1357743/am386de-33kc_amd-advanced-micro-devices.html AMD (Advanced Micro Devices) AM386DE-33KC 32-BIT, 33 MHz, MICROPROCESSOR, PQFP132 pdf datasheet ]}}
{{AMD_processors}}
Am386 Category:X86 microarchitectures Category:Computer-related introductions in 1991