IMUL - Signed Multiply

        Usage:  IMUL    src
                IMUL    src,immed        (286+)
                IMUL    dest,src,immed8  (286+)
                IMUL    dest,src         (386+)
        Modifies flags: CF OF (AF,PF,SF,ZF undefined)

        Signed multiplication of accumulator by src with result placed
        in the accumulator.  If the source operand is a byte value, it
        is multiplied by AL and the result stored in AX.  If the source
        operand is a word value it is multiplied by AX and the result is
        stored in DX:AX.  Other variations of this instruction allow
        specification of source and destination registers as well as a
        third immediate factor.

                                  Clocks                Size
        Operands         808x   286   386   486         Bytes

        reg8             80-98   13   9-14  13-18         2
        reg16           128-154  21   9-22  13-26         2
        reg32              -     -    9-38  12-42         2
        mem8             86-104  16  12-17  13-18        2-4
        mem16           134-160  24  12-25  13-26        2-4
        mem32              -     -   12-41  13-42        2-4
        reg16,reg16        -     -    9-22  13-26        3-5
        reg32,reg32        -     -    9-38  13-42        3-5
        reg16,mem16        -     -   12-25  13-26        3-5
        reg32,mem32        -     -   12-41  13-42        3-5
        reg16,immed        -     21   9-22  13-26         3
        reg32,immed        -     21   9-38  13-42        3-6
        reg16,reg16,immed  -     2    9-22  13-26        3-6
        reg32,reg32,immed  -     21   9-38  13-42        3-6
        reg16,mem16,immed  -     24  12-25  13-26        3-6
        reg32,mem32,immed  -     24  12-41  13-42        3-6


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