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Architechture of 8086 or Functional Block diagram of 8086

  • 8086 has two blocks Bus Interfacing Unit(BIU) and Execution Unit(EU).
  • The BIU performs all bus operations such as instruction fetching, reading and writing operands for memory and calculating the addresses of the memory operands. The instruction bytes are transferred to the instruction queue.
  • EU executes instructions from the instruction system byte queue.
  • Both units operate asynchronously to give the 8086 an overlapping instruction fetch and execution mechanism which is called as Pipelining. This results in efficient use of the system bus and system performance.
  • BIU contains Instruction queue, Segment registers, Instruction pointer, Address adder.
  • EU contains Control circuitry, Instruction decoder, ALU, Pointer and Index register,Flag register.