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Architecture of 8087 Math co-processor

 

Introduction 

  • 8087 coprocessor is designed to operate with an 8086 microprocessor.
  • The microprocessor and coprocessor can execute their respective instructions simultaneously.
  • The microprocessor interprets and executes the normal instruction set and the coprocessor interprets and executes only the coprocessor instructions.
  • All the coprocessor instructions are ESC instructions i.e. they start with ''F'',

Architecture of 8087

The  internal structure of the 8087 coprocessor is divided into two major sections :
  • the control unit ( CU )
  • Numeric Execution Unit ( NEU )

Control Unit ( CU )

  • It interfaces the coprocessor to the microprocessor system bus.
  • It also synchronized the operation of the coprocessor and the microprocessor.
  • This unit has a control word, status word, and Data buffer.
  • If an instruction is ESC instruction, then the coprocessor executes it.
  • If not, then the microprocessor executes.

Numeric Execution Unit ( NEU )

  • This unit is responsible for executing all coprocessor instructions.
  • It has an 8-register stack that holds the operands for instruction and the result of instructions.
  • The stack contains 8 registers that are 80 bits wide.
  • Numeric data is transferred inside the coprocessor in two parts. 
    • 64-bit mantissa bus.
    • 16-bit exponent bus.


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