An Intel 80186 Microprocessor
|Produced||From 1982 to 2007|
|Max. CPU clock rate||6 MHz to 25 MHz|
The Intel 80186 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 chips 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 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 included in the 80286 and successor chips.
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 PC-D (not 100% IBM PC-compatible but using MS-DOS 2.11 de:Siemens PC-D); the Compis (a Swedish school computer); 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 Philips :YES; the Nokia MikroMikko 2. Acorn created a plug-in for the BBC Master range of computers containing a 80186-10 with 512 KB of RAM, the 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 16MHz 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. Pin- and instruction-compatible replacements might still be manufactured by various 3rd party sources.
Notes and references 
- In fact, all variants, including reg+reg and reg+reg+immediate were faster.
- "Intel cashes in ancient chips".
- "Innovasic Offers Replacement ICs for Intel 186/188 Microcontrollers".
- Intel Datasheet
- Scan of the Intel 80186 data book at datasheetarchive.com
- Intel 80186/80188 images and descriptions at cpu-collection.de