[djmips]

Yeah, the algorithm is only thousands of years old but it's very useful on the 6502. See 'Fast Signed Multiply' at http://www.ffd2.com/fridge/chacking/c=hacking9.txt for an implementation in C64 3D routines.

Also note that this algorithm was used in analog electronics to multiply. https://patents.google.com/patent/US2906459A/en