Name:		Henry Hoi Wai Chan
CSE Login:	hhwc896
Student Number: z3060374

Carry Look-ahead
+--------------+
4 Bit
=====
p(i)   = a(i) + b(i)
1T or gate
----------
1T

g(i)   = a(i) & b(i)
1T and gate
-----------
1T

c(i+1) = g(i) + p(i) & c(i)
1T propagate and generate
1T and gate
1T or gate
-------------------------
3T

sum(i) = fullerAdder(a(i),b(i),c(i))
3T carry
2T fullerAdder
--------------
5T

4x4 Bit
=======
P(i) = p(4i+3) & p(4i+2) & p(4i+1) & p(4i)
1T propagate
1T and gate
------------
2T

G(i) = g(4i+3)+(g(4i+2)&p(4i+3))+(g(4i+1)&p(4i+2)&p(4i+3))+(g(4i)&p(4i+1)&p(4i+2)&p(4i+3))
1T propagate and generate
1T and gate
1T or gate
-------------------------
3T

Ci+1 = Gi + Pi & Ci
3T generate but 2T propagate
1T and gate
1T or gate
----------------------------
5T

SUM = 4BitAdder(A,B,C)
5T carry
5T fullerAdder
--------------
10T



Carry Save
+--------+

 A   B   E   F
 |   |   |   |
 |   V   V   V
 |  +----------+
 |  |Carry Save|
 |  +----------+
 |   |   |
 V   V   V
+----------+
|Carry Save|
+----------+
  |C'    |S'
  V      V
+-----------------+
|Traditional Adder|
+-----------------+
         |
         V
         S

Since all 4 adders in the Carry Save runs in parallel
2T First Carry Save
2T Second Carry Save
8T Traditional Adder
--------------------
12T



Summary
+-----+
Carry Lookahead =  5T
Carry Save	= 12T