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by JoshTriplett 2273 days ago
> To implement 32-bit + in hardware you need 31 full adders and one half adder, each of which uses multiple gates and depends on the result of the previous adder.

This is not how CPUs typically implement addition, or other ALU operations. Carry-lookahead adders have existed since the 1950s: https://en.wikipedia.org/wiki/Carry-lookahead_adder

1 comments

Thank you, I love this citation so much.

> Charles Babbage recognized the performance penalty imposed by ripple-carry and developed mechanisms for anticipating carriage in his computing engines.