If I'm using the '181, I could make all functions available to the compiler. I mean, there could be some efficiency gains in the more obscure functions. Since there's 4 bits for the function select pins, one for the mode pin, and a carry input, that's 6 control inputs. So I could have a separate address for each of the 2^6 or 64 possible functions. If only have 256 locations available for the 8-bit address bus, and half will be taken up by my RAM. So 128-64 = 64 remaining addresses. Should be plenty. It shouldn't be too difficult to decode considering I can take those 6 bits from the address line and run them straight to the ALU. It's a big gain for very little investment.