Problem: ripple carry adder is slow
Is a 32-bit ALU as fast as a 1-bit ALU?
Is there more than one way to do addition?
- two extremes: ripple carry and sum-of-products
Can you see the ripple? How could you get rid of it?
c2 = b1c1 + a1c1 + a1b1 c2 =
c3 = b2c2 + a2c2 + a2b2 c3 =
c4 = b3c3 + a3c3 + a3b3 c4 =