ALU

ALU: Arithmetic Logic Unit

• Circuit that does logical and arithmetic operations. (e.g., AND, NOR, addition, division).

On Speed v.s. Complexity:

• We can derive universal gates from an extremely simple add-only ALU, but the tradeoff is speed.

Example: Universal Gates from Simple ALU

Within this simple adder-only ALU, we can see that:

• The carry bit acts as a 2AND
• The sum bit acts as a 2XOR
  • Further, wiring a 2XOR such that the two inputs going in are A and 1, the result will be \bar{A}
    • This lets is do NAND, which is a universal gate.