ALU: k-bit

To operate on k-bit values,

we can connect k 1-bit ALU's

32-bit ALU is constructed using 32

1-bit ALU's

Input bits are connected in pairs

Control bits (Binvert, Operation)

are connected to each ALU

cout from each ALU is connected to

cin of next most significant bit ALU

(ripple carry)

cin for lsb is 1 for subtract operation

Set from ALU31 (msb) is connected

to Less input of ALU0 (lsb)

(0 input for all other ALUs)

Overflow from ALU31 is additional output

32-bit ALU (Fig. 4.18)