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Intel 80186

Intel 80186
An Intel 80186 Microprocessor
Produced From 1982 to 2007
Max. CPU clock rate 6 MHz to 25 MHz
Instruction set x86-16
Model 80186 Series
Predecessor 8088
Successor 80386 (The 80286 was also introduced in early 1982, and thus contemporary with the 80186)
Variant 80188
File:Intel 80186 80188 arch.svg
A greatly simplified block diagram of the 80186 architecture.

The Intel 80186 ("eighty-one-eighty-six"), also known as the iAPX 186,[1] or just 186 ("one-eighty-six" or "one-eight-six"), is a microprocessor and microcontroller introduced in 1982. It was based on the Intel 8086 and, like it, had a 16-bit external data bus multiplexed with a 20-bit address bus. It was also available as the 80188, with an 8-bit external data bus.


Features and performance

The 80186 series was generally intended for embedded systems, as microcontrollers with external memory. Therefore, to reduce the number of integrated circuits required, it included features such as clock generator, interrupt controller, timers, wait state generator, DMA channels, and external chip select lines.

The initial clock rate of the 80186 was 6 MHz, but due to more hardware available for the microcode to use, especially for address calculation, many individual instructions ran faster than on an 8086 at the same clock frequency. For instance, the common register+immediate[2] addressing mode was significantly faster than on the 8086, especially when a memory location was both (one of the) operand(s) and the destination. Multiply and divide also showed great improvement being several times as fast as on the original 8086 and multi-bit shifts were done almost four times as quickly as in the 8086.

A few new instructions were introduced with the 80186 (referred to as the 8086-2 instruction set in some datasheets): enter/leave (replacing several instructions when handling stack frames), pusha/popa (push/pop all general registers), bound (check array index against bounds), and ins/outs (input/output of string). A useful immediate mode was added for the push, imul, and multi-bit shift instructions. These instructions were also included in the contemporary 80286 and in successor chips.

The (redesigned) CMOS version, 80C186, introduced DRAM refresh, a power-save mode, and a direct interface to the 8087 or 80187 floating point numeric coprocessor.


In personal computers

The 80186 would have been a natural successor to the 8086 in personal computers. However, because its integrated hardware was incompatible with the hardware used in the original IBM PC, the 80286 was used as the successor instead in the IBM PC/AT.

Few personal computers used the 80186, with some notable exceptions: the Australian Dulmont Magnum laptop, one of the first laptops; the Wang Office Assistant, marketed as a PC-like stand-alone word processor; the Mindset; the Siemens [[Siemens PC-D#REDIRECTmw:Help:Magic words#Other
This page is a soft redirect.PC-D]] (de) (not 100% IBM PC-compatible but using MS-DOS 2.11); the Compis (a Swedish school computer); the French SMT-Goupil G4; the RM Nimbus (a British school computer); the Unisys ICON (a Canadian school computer); ORB Computer by ABS; the HP 100LX, HP 200LX, HP 1000CX, and HP OmniGo 700LX; the Tandy 2000 desktop (a somewhat PC-compatible workstation with sharp graphics for its day); the Telex 1260 (a desktop PC-XT compatible); the Philips :YES; the Nokia MikroMikko 2. Acorn created a plug-in for the BBC Master range of computers containing an 80186-10 with 512 KB of RAM, the BBC Master 512 system.

Other devices

The Intel 80186 was intended to be embedded in electronic devices that are not primarily computers. For example, its offshoot, Intel 80188 was embedded inside the Intel 14.4EX modem released in 1991. The 16 MHz processor was used to perform complex algorithms needed for forward error correction, Trellis coded modulation, and echo cancellation in the modem.

In May 2006, Intel announced that production of the 186 would cease at the end of September 2007.[3] Pin- and instruction-compatible replacements might still be manufactured by various third party sources.[4]

See also

  • iAPX, for the iAPX name

Notes and references

  1. ^ Official Intel iAPX 286 programmers' manual (page 1-1)
  2. ^ In fact, all variants, including reg+reg and reg+reg+immediate were faster.
  3. ^ "Intel cashes in ancient chips". 
  4. ^ "Innovasic Offers Replacement ICs for Intel 186/188 Microcontrollers". 
  • Attribution: This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.

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