The third section of the ALU is the ability to compare two numbers and output either 0 or 1 depending on if the first value is less than the second. It has the extra complication of allowing comparison of signed and unsigned numbers.

Implementation is simple enough as it is just a cut down version of the full compare board I have already created elsewhere.  It needs two boards stacked in the usual vertical fashion using long female headers. It uses 4 x 76HC682 8bit comparators and then a little gate logic to determine the result. Unfortunately there is a just a little too much logic to fit on a single board.