The radix 2^51 trick (2017)
What I'm wondering about now is: does that 'adc' opcode have any other useful application except for adding numbers bigger than the width of a single register?<p>Because it does look a little bit as if it was engineered for that particular situation, and if that was the case, with this situation now in practice being solved much more efficiently without a single 'adc' instruction, the opcode might suddenly be completely useless bloat - which of course still had to be maintained forever, even though nobody uses it in practice, because it's part of the spec.