Earlier quoted context omitted.
The work started around 10-15 years ago and is now largely done. Many people confuse large absolute numbers like 1 kW with inefficiency but today's GPUs/TPUs are close to the practical efficiency limit with today's 3 nm technology.
I think it's mostly because laypeople think that all heat is wasted heat. Most people are pretty surprised to learn that there's a fundamental energy cost to flip a bit and that there even is a lower limit to the amount of heat generated by a bit flip.
The carnot cycle on waste heat is bad