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     See also: Register/Memory (r/m) Field, Scaled Index Mode
 
     The two-bit mode (mod) field gives the register/memory (r/m)
     addressing mode.
 
     mod    Description
 
     00     If r/m is 110, a direct memory operand is used; otherwise,
            an indirect memory operand is used with a zero
            displacement. The operand must be based, indexed, or based
            indexed.
 
     01     An indirect memory operand is used with an 8-bit
            displacement.
 
     10     An indirect memory operand is used with a 16-bit
            displacement.
 
     11     Instruction is register-to-register. The reg field
            specifies the destination, and the r/m field specifies the
            source.
 
     In 32-bit mode, 00, 01, and 11 in the mode field have different
     meanings.
                                    -♦-