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PCMPEQB         Packed Compare for Equal, Byte

PCMPEQB destination, source                          CPU: MMX

        Logic   if mm(7..0)   = mm/m64(7..0)
                     mm(7..0)   <- 0FFh
                else mm(7..0)   <- 0
                endif
                if mm(15..8)  = mm/m64(15..8)
                     mm(15..8)  <- 0FFh
                else mm(15..8)  <- 0
                endif
                if mm(23..16) = mm/m64(23..16)
                     mm(23..16) <- 0FFh
                else mm(23..16) <- 0
                endif
                if mm(31..24) = mm/m64(31..24)
                     mm(31..24) <- 0FFh
                else mm(31..24) <- 0
                endif
                if mm(39..32) = mm/m64(39..32)
                     mm(39..32) <- 0FFh
                else mm(39..32) <- 0
                endif
                if mm(47..40) = mm/m64(47..40)
                     mm(47..40) <- 0FFh
                else mm(47..40) <- 0
                endif
                if mm(55..48) = mm/m64(55..48)
                     mm(55..48) <- 0FFh
                else mm(55..48) <- 0
                endif
                if mm(63..56) = mm/m64(63..56)
                     mm(63..56) <- 0FFh
                else mm(63..56) <- 0
                endif

    PCMPEQB compares the bytes in the destination operand to the
    corresponding bytes in the source operand. If the data elements are
    equal, the corresponding data element in destination is set to all
    ones. If they are not equal, the corresponding data element is set
    to all zeros. 

    The destination operand is an MMX register. The source operand can
    either be an MMX register or a 64-bit memory operand.


    Opcode      Format
    0F 74 /r    PCMPEQB mm/m64