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Can ALU Input be register?

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  1. Mar 1, 2017 #1
    In CPU ALU (arithmetic logic unit ) has two input.
    If one of the input has following Input LDA #23 this input will be stored in eax register.
    mov eax, 23d
    when do i need to use 2 of these input? Can any of this input be a Register ?
     
    Last edited: Mar 1, 2017
  2. jcsd
  3. Mar 2, 2017 #2
    If you talk about eax, I suppose you're talking about an intel 80386 or a successor. With this processor you can use a register, memory or an immediate operand for both operands of the alu, or for the destination. but only one memory operand for each instruction.
    you can do: add eax, 117 or add ecx, ebx or add eax, [esi] or add [memory_address],12
    but not add [memory_address1],[memory_address2]
     
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