Hey Gil, I assume that type of math with bits is super fast ...I has a friend show my similar techniques using SRL or SLL, but my old age ...I forgot . Will have to revisit
Scott ford www.identityforge.com from my IPAD 'Infinite wisdom through infinite means' On Apr 17, 2013, at 1:03 PM, Paul Gilmartin <paulgboul...@aim.com> wrote: > On 2013-04-17, at 09:31, DASDBILL2 wrote: > >> I tried your algorithm with 13 multiplied by 81 and produced the correct >> answer. This algorithm is undoubtedly how the microcode for the M (multiply >> fullword) instruction does its math. > It has a lot to do with where the 1-bits are in the binary representation > of the multiplier, yes. > > GIYF. "Wallace tree" > > PDP-6 et al. inspected two bits of the multiplier at each iteration > and mixed adds and subtracts to get a 2s complement product without > a restoring step. > >> ----- Original Message ----- >> From: "Gerhard Postpischil" >> Sent: Wednesday, April 17, 2013 10:19:22 AM >> >> Simple - you write the two numbers with the larger on the left. In the >> next row, double the number on the left, and halve the number on the >> right, discarding any fraction. Upon reaching 1 on the right, cross out >> any row where the right number is even. Add the remaining rows on the left. > > -- gil
