Intel 80186

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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 Intel 80188, with an 8-bit external data bus.



Features and performance

The 80186 and 80188 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 and 80188 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[1] 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 fast than 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), 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.

The (redesigned) CMOS version, 80C186, introduced DRAM refresh, a power-save mode, and a direct interface to the 8087 or 80287 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 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 200lx; the Tandy 2000 desktop (a somewhat PC-compatible workstation with sharp graphics for its day); the Philips :YES. 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.

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