Booth:
  result = multiplier << 1
  loop (operand length) times:
    if last two bits are 01:
      result(upper half) += multiplicand
    if last two bits are 10:
      result(upper half) += twos_comp(multiplicand)
    remove extra bits from result
    arithmatic shift result right
  result >> 1

Modified booth:
  multiplicand(MSB) = multiplicand(second MSB)
  result = multiplier << 1
  loop (operand length / 2) times:
    if last two bits are 001 or 010:
      result(upper half) += multiplicand
    if last two bits are 011:
      result(upper half) += multiplicand * 2
    if last two bits are 100:
      result(upper half) += twos_comp(multiplicand) * 2
    if last two bits are 101 or 110:
      result(upper half) += twos_comp(multiplicand)
    remove extra bits from result
    arithmatic shift result right twice
  result >> 1
  result(second MSB) = result(MSB)
  result(MSB) = 0