How to fix computing’s AI energy problem: run everything backwards

Imagine taking a hammer to your laptop. You smash it apart and shards of plastic, batteries and circuit board go flying. It would be an act of vandalism, a shocking waste of money and resources, so much so that it sounds absurd. But the truth is that, every time we use a computer, we are dealing with a machine that is, at the fundamental level, even more wasteful than this.

It all goes back to a decision made decades ago about the deep workings of computer logic and how these machines delete data, a process that inevitably produces a large amount of waste heat. For a long time, we have muddled through with wasteful computers. But with the rise of artificial intelligence, which has pushed the power demands of computing to new heights, this seemingly inconsequential decision might be about to bite us. We may need to redesign computing from scratch.

Thankfully, we know exactly what to do. It involves a trick that might sound a touch unlikely: getting processors to do everything twice, once forwards, then in reverse. “Reversible computing can be so much more energy efficient than conventional computing, and it’s potentially the way we should have originally built computers,” says Hannah Earley at UK-based reversible computing company Vaire Computing.

The increased energy efficiency is the result of a thermodynamic trick that we have known about since the 1970s, but was never put into use because of the…