Building the full adder might even make it less ICs overall. Lots of tricks are lost here, for example the subtraction logic can be used to implement a NOT func

Building the full adder might even make it less ICs overall. Lots of tricks are lost here, for example the subtraction logic can be used to implement a NOT function if you add to zero. Rather than having an extra XOR chip you can implement XOR by using the adder but cutting the cout->cin path. The 74x181 4-bit ALU IC implements all of this (plus quite a lot more) in 56 gates once you drop the carry-lookahead logic. That'd be about the same number of ICs as used in this project, but logic only. http://www.ti.com/lit/ds/symlink/sn74ls181.pdf http://www.ti.com/lit/ds/symlink/sn74ls181.pdf (page 5)