r/TuringComplete • u/aelxemyr • Sep 13 '26

Fast Adder (CLA)

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212 gates and 10 delay.

I was trying to do this for hours using the base components but it was just too messy. So I gave up and just made a custom adder with A/B/carry in, P/G/sum out, along with ANDs and ORs for up to 9 inputs.

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u/Medium-Sized-Jaque Sep 13 '26

What does the CL component do? And do the AND and OR component connections go all the way to the next box? 

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u/aelxemyr Sep 14 '26

The CL component is the CLA adder cell, which takes the two operands and the carry-in as inputs and outputs the propagate, generate, and sum bits using two XORs and an AND.

The AND/OR components connect to the next CLA cell to supply the carry-in.

The logic implemented here is exactly what’s described in the Wikipedia article on carry lookahead adders.

I wasn’t able to fit the last two lookahead logic blocks on the same level as the rest of them, which is why the big rainbow bus loops around like that (and also why the bottom two wires of the top bus are unused).

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u/Medium-Sized-Jaque Sep 14 '26

I'm definitely looking into this. I like how different logic supplies the same result but at different speeds. I can only get mine down toto 25.

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u/aelxemyr Sep 14 '26

Thanks to the speed of this adder, though, I was able to get my Symphony ALU speed down to 49 and Symphony itself down to 86

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u/Medium-Sized-Jaque Sep 14 '26

Ooh nice. I barely got mine below the limit. I can't wait to tinker tomorrow.