Effective Address (EA) Calculations
 
    This table lists the number of clock cycles required to calculate the
    effective address on the 8088 microprocessor.  The 80x8x processors
    require considerably fewer clock cycles to calculate effective
    addresses, so this table represents the worst-case.
 
  --------------------------------------------------------------------------
    EA Component                  8088 Clocks          Example
    Displacement                       6               MOV AX,ADDR
 
    Register indirect                  5               MOV AX,[BP]
        BX, BP, SI, DI
 
    Displacement + Base or Index       9               MOV AX,ADDR[BP]
        BX + Disp, BP + Disp
        SI + Disp, DI + Disp
 
    Base + Index
        BP + DI, BX + SI               7               MOV AX,[BP+DI]
        BP + SI, BX + DI               8               MOV AX,[BX+DI]
 
    Displacement + Base + Index
        BP + DI + Disp                 11              MOV AX,ADDR[BP+DI]
        BX + SI + Disp
 
        BP + SI + Disp                 12              MOV AX,ADDR[BP+SI]
        BX + DI + Disp
  --------------------------------------------------------------------------
 
       Notes:         Add 2 clocks for segment overrides
 
                      Each memory reference requires an additional 4 clock
                      cycles.  The Transfers field in the instruction
                      timing charts gives the number of memory references
                      for each instruction.

This page last updated on Fri Nov 30 10:49:50 MSK 2001
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