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.


Assembly - Effective Address