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Intel 8086 processors

The Intel 8086

In 1978, Intel(Integrated Electronics) came out with the 8086 processor. The Intel 8086 is a 16-bit microprocessor, implemented in N-channel, depletion load, silicon gate technology(HMOS), and packaged it in a 40 pin dual in line package. In this blog , we study  fearures, architecture, register organisarion, bus operation and memory segmentation etc.

Features of 8086

  1. The 8086 is a 16-bit microprocessor. The term "16-bit" means that its arithmetic logic unit, internal registers and most of its instructions are designed to work with 16-bit binary words.
  2. The 8086 has a 16-bit data bus, so it can read data from or write data to memory and ports either 16 bits or 8 bits at a time.
  3.  The 8086 has a 20-bit address bus, so it can directly access 220 or 10,48,576 (1Mb) memory locations. Each of the 10,48,576 memory locations is byte wide. Therefore the 16-bit words are stored in two consecutive memory locations.
  4. The 8086 can generate 16-bit I/O address, hence it can access 216= 65536 I/O  ports.
  5. The 8086 provides fourteen 16-bit registers.
  6.  The 8086 has multiplexed address and data bus which reduces the number of pins needed, but does slow down the transfer of data (It is a drawback).
  7. The 8086 requires one phase clock with a 33% duty cycle to provide optimized   internal timing.
  8. The 8086 is possible to perform bit, byte, word and block operarions in 8086. It perform, the arithmetic and logical operations on bit, byte, word and decimal numbers including multiply and divide.
  9. The Intel 8086 is designed to operate in two modes, namely the minimum mode and the maximum mode. When only one 8086 CPU is to be used in a microcomputer system, the 8086 is used in the minimum mode of operation. In this mode the CPU issues the control signals required by memory and I/O devices. In multiprocessor (more than one processor in the system) system 8086 operates in maximum mode. In maximum mode, control signals are generated with the help of external bus controller (8288).
  10. The Intel 8086 supports multiprogramming. In multiprogramming, the code for two or more processes is in memory at the same time and is executed in a time-multiplexed fashion.
  11. An interesting feature of the 8086 is that it fetches up to 6 instruction bytes from memory and queue stores them in order to speed up the instruction execution.
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