Don't think of it as billions of pieces each added one at a time, think of it as teeth in a comb, all made at once, in parallel. Either the whole part works pr

Don't think of it as billions of pieces each added one at a time, think of it as teeth in a comb, all made at once, in parallel. Either the whole part works properly (during testing), or, if only a few cores work, the defective portions are disabled permanently, or if none work, it is thrown away. Typical yields for a given silicon production line start at a few percent, and go up towards 100% as much as the process improvement allows.