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  • 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 ??
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Replies

  • Nayan Goenka

    Member • Aug 11, 2013

    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.
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  • Kaustubh Katdare

    Administrator • Aug 11, 2013

    Thread Moved to Electronics engineering section.
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  • Teresan

    Member • Aug 11, 2013

    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..
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  • Cyborg 009

    Member • Aug 12, 2013

    Kogge-Stone adder...fastest adder design possible.
    Manchester carry chain...
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  • Teresan

    Member • Aug 12, 2013

    Cyborg 009
    Kogge-Stone adder...fastest adder design possible.
    Manchester carry chain...
    Thank you ..
    Can you explain what is Kogge stone adder is ?
    And how it works?
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  • Cyborg 009

    Member • Aug 12, 2013

    variation of carry look ahead...
    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)))
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  • Teresan

    Member • Aug 12, 2013

    Cyborg 009
    variation of carry look ahead...
    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 😀
    Thanks alot.. I will include it in my project..
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  • Nayan Goenka

    Member • Aug 12, 2013

    Cyborg 009
    Kogge-Stone adder...fastest adder design possible.
    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.
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  • Jeffrey Arulraj

    Member • Aug 12, 2013

    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
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  • Cyborg 009

    Member • Aug 12, 2013

    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.
    4_bit_Kogge_Stone_Adder_Example_new
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  • kheerthi chandru

    Member • Aug 19, 2013

    Cyborg 009
    Kogge-Stone adder...fastest adder design possible.
    Manchester carry chain...

    can u explain about Manchester carry chain ?
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  • Jeffrey Arulraj

    Member • Aug 19, 2013

    kheerthi chandru
    can u explain about Manchester carry chain ?
    #-Link-Snipped-#

    This tells us in detail about the carry chain adders Do read the article and post your queries here
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  • kheerthi chandru

    Member • Sep 23, 2013

    i need coding fr carry skip adder. if any1 can search for it please post it as soon as possible. little urgent
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  • Jeffrey Arulraj

    Member • Sep 23, 2013

    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
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  • Jeffrey Arulraj

    Member • Sep 23, 2013 

    
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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