Adder comparisons and New (1,1,1)adder

Peeyush Pashine

2011H140033H

Brent Kung adder

Sklansky adder

c1

(p2, g2)(p3, g3)(p4, g4)(p5, g5)(p6, g6)(p7, g7)(p8, g8)

c2c3c4c5c6c7c8

(p1, g1)

Skalnsky adder 16 bit

1:

0

2:

0

3:

0

3:

2

5:

4

7:

6

9:

8

11:1

0

13:1

2

15:1

4

6:

4

7:

4

10:

8

11:

8

14:1

2

15:1

2

12:

8

13:

8

14:

8

15:

8

0123456789101112131415

15:014:013:0 12:011:010:0 9:0 8:0 7:0 6:0 5:0 4:0 3:0 2:0 1:0 0:0

Ladner fischer adder

1:03:25:47:69:811:1013:12

3:07:411:815:12

5:07:013:815:8

15:14

15:8 13:0 11:0 9:0

0123456789101112131415

15:0 14:013:012:0 11:010:0 9:0 8:0 7:0 6:0 5:0 4:0 3:0 2:0 1:0 0:0

Kogge stone adder

1:02:13:24:35:46:57:68:79:810:911:1012:1113:1214:1315:14

3:04:15:26:37:48:59:610:711:812:913:1014:1115:12

4:05:06:07:08:19:210:311:412:513:614:715:8

2:0

0123456789101112131415

15:014:013:0 12:011:010:0 9:0 8:0 7:0 6:0 5:0 4:0 3:0 2:0 1:0 0:0

7

Classical prefix adders

12345678

12:13:14:16:17:18:1 5:1

Brent-Kung:

Logical levels: 2log2n–1

Max fanouts: 2

Wire tracks: 1

12345678

12:13:14:16:17:18:1 5:1

Kogge-Stone:

Logical levels: log2n

Max fanouts: 2

Wire tracks: n/2

12345678

12:13:14:16:17:18:1 5:1

Sklansky:

Logical levels: log2n

Max fanouts: n/2

Wire tracks: 1

Knowles 2,1,1,1

Knowles 4,2,1,1

Topology of some prefix adders

Brent-Kung topology(Minimum fan-out)

Ladner-Fischer topology(Minimum depth, high fanout)

Knowles topologies(Varied fan-out at each level )

Prefix adder taxonomy

New (1,1,1) Adder

2345678

2:13:14:16:17:18:1 5:1

19101112

19:110:111:112:1