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Is there a type of adder faster than carry look ahead adder?

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matrixofdynamism

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I want to know ALL the different type of arithmatic circuits used in digital circuit design arranged per speed. Here I am talking about adders and multipliers. As far as I know the subtractor is merely created from the adder itself by merely using 2s complete of the second operand.

I am not aware of any adder faster than the carry look ahead adder.

Is there a resource that explains what type of arithmatic circuit is faster for what size of operands and how does one actually determine how fast a given arithmaitc circuit is.
 

jt_eaton

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A ripple carry adder is faster than a carry look ahead adder.

I know this is exactly opposite of what is taught in school but welcome to the work of deep sub micron processes.

If you lay out a ripple carry adder so that you minimize the length of the carry chain then it will result in a very tight and compact layout. Any attempt to route the carry away from this layout, through some logic and then back will cost more in transport delay than you save from gate delay.

John Eaton
 

matrixofdynamism

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Hmmm.. I have never seen or heard of this Kogge–Stone adder before. Strange.

...and what jt_eaton said is even more strange.
 

matrixofdynamism

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OK, I take this to mean since a subtractor is merely an adder with one of the operands inverted and the carry input always tied high, it means that the Kogge-Stone adder can be used to create the fastest subtractor too.
 

Ashish Harkut

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I want to know ALL the different type of arithmatic circuits used in digital circuit design arranged per speed. Here I am talking about adders and multipliers. As far as I know the subtractor is merely created from the adder itself by merely using 2s complete of the second operand.

I am not aware of any adder faster than the carry look ahead adder.

Is there a resource that explains what type of arithmatic circuit is faster for what size of operands and how does one actually determine how fast a given arithmaitc circuit is.

please post the parallel prefix adder code
 
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