Note that in Allison's Algorithm, that second ADD should actually be an ADC. (I say this both because that's what's in the original paper and because checking

Note that in Allison's Algorithm, that second ADD should actually be an ADC. (I say this both because that's what's in the original paper and because checking it myself that's what works -- it's needed to add the 1 for A through F, so you don't get @ through E instead. Didn't check the second one.)