PPT Slide
Cost of different logic functions
Different functions are easier or harder to implement
- each has a cost associated with the number of switches needed
- 0 (F0) and 1 (F15): require 0 switches, directly connect output to low/high
- X (F3) and Y (F5): require 0 switches, directly connect output to one of inputs
- X' (F12) and Y' (F10): require 2 switches for "inverter" or NOT-gate
- X nor Y (F4) and X nand Y (F14): require 4 switches
- X or Y (F7) and X and Y (F1): require 6 switches
- X = Y (F9) and X ° Y (F6): require 16 switches
- thus, because NOT, NOR, and NAND are the cheapest they are the functions we implement the most in practice