An 8 bits "ALU" with 5 instructions:
ADD xxx0 0001
SUB xxx0 0010
AND xxx0 0100
OR xxx0 1000
NOT xxx1 0000 ;Invert bits from A
This one doesn't have an accumulator, so every instruction you will loose all the information from A and B, but works with way less lag.
Shortened version (just ADD and SUB operations):
https://everycircuit.com/circuit/6299875167436800
4 bits ALU (with an accumulator):
https://everycircuit.com/circuit/5333449376006144
