Carry Look-Ahead Adder

240

02:07:06

So, @hurz, you thought that my ripple carry adder was too slow for you? Well, look at my brand new Carry Look-Ahead Adder! The red displays are the inputs, and the green display is the output. The two columns of logic sources on the top-left are the input, the logic source on the bottom-left is the carry-in input, and the decimal point on the output is the carry-out output. It's much more complex than my ripple carry adder. Also, I changed a these things in the schematic I was copying from to make it simpler: I didn't put in any buffer gates, and I changed a few gates to XOR.

published 8 years ago

hurz

8 years ago

What is the msg? Is it this one is even alower? How much slower?

jason9

8 years ago

There isn't really a message, I just decided to make a carry look-ahead adder because you told me that my other ripple carry adder was slow. This one is probably faster, but is more complex, which creates more lag in the simulator.

hurz

8 years ago

How much faster, do you think its with look ahead?

jason9

8 years ago

I don't know for sure, but I can do some math. So, this circuit has four gates (ideally, but I have to use AND gates in series to make AND gates with more than two inputs) between the inputs and the outputs, and, depending on which input it is, the ripple carry adder has anywhere between 1-12 gates between the input and the output. I'm very unsure about the numbers on the ripple carry adder. This means that if the ripple carry adder has an average of 6 gates between the input and output, and a carry look-ahead adder has 4 gates between the input and output, the carry look-ahead adder will process the numbers at 150% speed, if the ripple carry adder is considered to be at 100% speed. I guess that means it's 50% faster.

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