Hi,
I am doing my mini project on the topic VLSI implementation of adders for high speed ALU
We are comparing various adders like Carry save, carry select, carry skip, Ripple carry and carry look ahead adder on their performances upto 32 bits using XILINX software version 9.1.
Is their any other adder which can be included that has the high speed when compared to those mentioned above ??

## Replies

• Nayan Goenka
I studied BCD adders too in the topic of Adders and I guess you are missing that. If you are including all adders, then BCD can also be included. I am not sure about its speed constraint though.
• Kaustubh Katdare
Thread Moved to Electronics engineering section.
• Teresan
Hi, I am not including BCD adders. Am selective in choosing the HSA (high speed adders) I chose only carry select,save and skip and concluded that carry select has the good speed capability..
I just wanna know about others...
I ll find out the speed capability of BCD adder too..
• Cyborg 009
Manchester carry chain...
• Teresan
Cyborg 009
Manchester carry chain...
Thank you ..
Can you explain what is Kogge stone adder is ?
And how it works?
• Cyborg 009
expansion for 4bit kogge stone..
Si= Pi XOR Ci-1
S0 = (A0 XOR B0) XOR Cin
S1 = (A1 XOR B1) XOR (A0 AND B0)
S2 = (A2 XOR B2) XOR (((A1 XOR B1) AND (A0 AND B0)) OR (A1 AND B1))
S3 = (A3 XOR B3) XOR ((((A2 XOR B2) AND (A1 XOR B1)) AND (A0 AND B0)) OR (((A2 XOR B2) AND (A1 AND B1)) OR (A2 AND B2)))
S4 = ((((A3 XOR B3) AND (A2 XOR B2)) AND (A1 AND B1)) OR (((A3 XOR B3) AND (A2 AND B2)) OR (A3 AND B3)))
• Teresan
Cyborg 009
expansion for 4bit kogge stone..
Si= Pi XOR Ci-1
S0 = (A0 XOR B0) XOR Cin
S1 = (A1 XOR B1) XOR (A0 AND B0)
S2 = (A2 XOR B2) XOR (((A1 XOR B1) AND (A0 AND B0)) OR (A1 AND B1))
S3 = (A3 XOR B3) XOR ((((A2 XOR B2) AND (A1 XOR B1)) AND (A0 AND B0)) OR (((A2 XOR B2) AND (A1 AND B1)) OR (A2 AND B2)))
S4 = ((((A3 XOR B3) AND (A2 XOR B2)) AND (A1 AND B1)) OR (((A3 XOR B3) AND (A2 AND B2)) OR (A3 AND B3)))
Yeah i get it ðŸ˜€
Thanks alot.. I will include it in my project..
• Nayan Goenka
Cyborg 009
Manchester carry chain...

That really seems a good example. do you happen to have any link or diagram of this type of adder? That will help understand the algorithm. The ANDs and ORs might be a bit confusing. you can also give an image from your notebook if you happen to have drawn any.
• Jeffrey Arulraj
Nayan Goenka
I studied BCD adders too in the topic of Adders and I guess you are missing that. If you are including all adders, then BCD can also be included. I am not sure about its speed constraint though.
BCD adders can be implemented using existing high speed adders and they just need another stage to compensate and balance the answer
• Cyborg 009
Nayan Goenka
That really seems a good example. do you happen to have any link or diagram of this type of adder? That will help understand the algorithm. The ANDs and ORs might be a bit confusing. you can also give an image from your notebook if you happen to have drawn any.
• kheerthi chandru
Cyborg 009
Manchester carry chain...

can u explain about Manchester carry chain ?
• Jeffrey Arulraj
kheerthi chandru
can u explain about Manchester carry chain ?

• kheerthi chandru
i need coding fr carry skip adder. if any1 can search for it please post it as soon as possible. little urgent
• Jeffrey Arulraj
kheerthi chandru
i need coding fr carry skip adder. if any1 can search for it please post it as soon as possible. little urgent
Are you looking for the VHDL program of that adder or any other language

Be more specific that will help us in helping you better
• Jeffrey Arulraj
```
G(0) := a(0) and b(0);
P(0) := a(0) or b(0);
C(1) := G(0) or (P(0) and cin);
for i in 1 to R-1 loop
G(i) := a(i) and b(i);
P(i) := a(i) or b(i);
C(i+1) := G(i) or(P(i) and C(i));
end loop;
```
This is one way of getting it done

Do execute it and tell us the result

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