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[[tr:Intel 8086]]
[[zh:Intel 8086]]
 
 
==History==
====Background====
In 1972 Intel launched the [[Intel 8008|8008]], the first 8-bit microprocessor.<ref>using enhancement load [[pMOS]] logic (demanding 14V, achieving TTL-compatibility by having V<sub>CC</sub> at +5V and V<sub>DD</sub> at -9V)</ref> It implemented an [[instruction set]] designed by [[Datapoint]] corporation with programmable [[Computer terminal|CRT terminals]] in mind, that also proved to be fairly general purpose. The device needed several additional [[Integrated Circuit|IC]]s to produce a functional computer, in part due to its small 18-pin "memory-package", which ruled out the use of a separate address bus (Intel was primarily a [[DRAM]] manufacturer at the time).
 
Two years later, in 1974, Intel launched the [[Intel 8080|8080]],<ref>using non-saturated enhancement load [[nMOS]] logic (demanding a higher gate voltage for the load transistor-gates)</ref> employing the new 40-pin [[Dual in-line package|DIL package]]s originally developed for [[calculator]] ICs to enable a separate address bus. It had an extended instruction set that was [[source compatible|source]]- (not [[binary compatible|binary]]-) compatible with the 8008 and also included some 16-bit instructions to make programming easier. The 8080 device, often described as the first truly useful microprocessor, was eventually replaced by the [[depletion-load NMOS logic|depletion-load]] based [[Intel 8085|8085]] (1977) which could cope with a single 5V power supply instead of the three different operating voltages of earlier chips.<ref>made possible with depletion load nMOS logic (the 8085 was later made using HMOS processing, just like the 8086)</ref> Other well known 8-bit microprocessors that emerged during these years were [[Motorola 6800]] (1974), [[PIC microcontroller|Microchip PIC16X]] (1975), [[MOS Technology 6502]] (1975), [[Zilog Z80]] (1976), and [[Motorola 6809]] (1978), as well as others.
 
====The first x86 design====
The 8086 project started in May 1976 and was originally intended as a temporary substitute for the ambitious and delayed [[iAPX 432]] project. It was an attempt to draw attention from the less-delayed 16 and 32-bit processors of other manufacturers (such as [[Motorola]], [[Zilog]], and [[National Semiconductor]]) and at the same time to counter the threat from the [[Zilog Z80]] (designed by former Intel employees), which became very successful. Both the architecture and the physical chip were therefore developed rather quickly by a small group of people, and using the same basic [[microarchitecture]] elements and physical implementation techniques as employed for the slightly older [[Intel 8085|8085]] (and for which the 8086 also would function as a continuation).
 
Marketed as [[Source code compatibility|source compatible]], the 8086 was designed so that [[assembly language]] for the 8008, 8080, or 8085 could be automatically converted into equivalent (sub-optimal) 8086 source code, with little or no hand-editing. The programming model and instruction set was (loosely) based on the 8080 in order to make this possible. However, the 8086 design was expanded to support full 16-bit processing, instead of the fairly basic 16-bit capabilities of the 8080/8085.
 
New kinds of instructions were added as well; full support for signed integers, base+offset addressing, and self-repeating operations were akin to the [[Z80]] design<ref>[http://www.pcworld.com/article/146957/birth_of_a_standard_the_intel_8086_microprocessor.html Birth of a Standard: The Intel 8086 Microprocessor. Thirty years ago, Intel released the 8086 processor, introducing the x86 architecture that underlies every PC-Windows, Mac, or Linux-produced today], PC World, June 17, 2008</ref> but were all made slightly more general in the 8086. Instructions directly supporting [[nested function|nested]] [[ALGOL]]-family languages such as [[Pascal (programming language)|Pascal]] and [[PL/M]] were also added. According to principal architect ''Stephen P. Morse'', this was a result of a more software centric approach than in the design of earlier Intel processors (the designers had experience working with compiler implementations). Other enhancements included [[microcode]]d multiply and divide instructions and a bus-structure better adapted to future co-processors (such as [[Intel 8087|8087]] and [[Intel 8089|8089]]) and multiprocessor systems.
 
The first revision of the instruction set and high level architecture was ready after about three months,<ref>Rev.0 of the instruction set and architecture was ready in about 3 months, according to Morse.</ref> and as almost no CAD-tools were used, four engineers and 12 layout people were simultaneously working on the chip.<ref>Using [[rubylith]], light boards, rulers, electric erasers, and a [[digitizer]] (according to Jenny Hernandez, member of the 8086 design team, in a statement made on Intel's web-page for its 25th birthday).</ref> The 8086 took a little more than two years from idea to working product, which was considered rather fast for a complex design in 1976–78.
 
The 8086 was sequenced<ref>8086 used less microcode than many competitors designs, such as the MC68000 and others</ref> using a mix of random logic and [[microcode]] and was implemented using depletion-load nMOS circuitry with approximately 20,000 active [[transistors]] (29,000 counting all [[Read only memory|ROM]] and [[Programmable logic array|PLA]] sites). It was soon moved to a new refined nMOS manufacturing process called [[HMOS]] (for High performance MOS) that Intel originally developed for manufacturing of fast [[static RAM]] products.<ref>Fast static RAMs in MOS technology (as fast as bipolar RAMs) was an important product for Intel during this period.</ref> This was followed by HMOS-II, HMOS-III versions, and, eventually, a fully static [[CMOS]] version for battery-powered devices, manufactured using Intel's [[CHMOS]] processes.<ref>CHMOS is intels name for CMOS circuits manufactured using processing steps very similar to [[HMOS]].</ref> The original chip measured 33&nbsp;mm² and minimum feature size was 3.2 μm.
 
The architecture was defined by ''[[Stephen Morse (designer)|Stephen P. Morse]]'' with some help and assistance by ''Bruce Ravenel'' (the architect of the 8087) in refining the final revisions. Logic designer ''Jim McKevitt'' and ''John Bayliss'' were the lead engineers of the hardware-level development team<ref>Other members of the design team were Peter A.Stoll and Jenny Hernandez.</ref> and ''William Pohlman'' the manager for the project. The legacy of the 8086 is enduring in the basic instruction set of today's personal computers and servers; the 8086 also lent its last two digits to later extended versions of the design, such as the [[Intel 286]] and the [[Intel 386]], all of which eventually became known as the [[x86]] family. (Another reference is that the [[PCI Configuration Space|PCI Vendor ID]] for Intel devices is 8086<sub>h</sub>!)
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