depending on the device and instruction set the swap is entirely free, e.g. where it's just a choice of a different load instructions (or the cool arches where

depending on the device and instruction set the swap is entirely free, e.g. where it's just a choice of a different load instructions (or the cool arches where you just make an unaligned read, the lsb triggers swapping). If energy is your concern making arches more energy efficient for swapping is the sensible thing as there are already many protocols and file formats in network order. There is fundamentally no reason for it to have a energy cost at all. And if you're really concerned about energy, the energy needed to communicate and store bits usually vastly dominates the energy needed to compute on them. On that basis protocols should be using varrious tightly packed / variable length encodings instead.