@steve@pkhuong@zwarich And that's when I finally folded and looked it up in Knuth and of course it's quite subtle: you can get away with looking at 3 leading digits of the dividend and 2 leading digits of the divisor, if you're in a power-of-two base, if you re-scale so the divisor's leading digit's MSB is 1, if you're okay with sometimes being off by 1 in the quotient estimate (which can be detected and fixed in one step). Probably got that wrong, but in any case it's not trivial.