Comment by JPLeRouzic

I wonder how this ALU works. From what I remember ALUs use lot of XOR gates because an adder is simply a network of XOR gates with carry propagation.

How could a NOR gate do one bit addition?

Add two bits ... XOR ... NOR

0 + 0 = 0...........0...........1

0 + 1 = 1...........1...........0

1 + 0 = 1...........1...........0

1 + 1 = 0...........0...........0