The Limits of Current Computing

The three limits to the performance of current (irreversible) computing.

People have mistakenly thought the physics limit is 1. not 2., below. This created the impression that reversible computing is something for a solution way off and not realizing that it actually solves for 3. which is an imminent problem.

1. Theoretical Scientific (Landauer) Limit — you can’t reduce energy per logical operation below this, even if you created a computer that used no energy to operate, or you would violate the laws of physics.

2. Actual Scientific Limit (below this would violate the laws of physics, in practice) — the Landauer limit plus additional energy that accounts for unavoidable real-world inefficiencies such as heat generated during the operation of a transistor, and other forms of energy dissipation like leakage.

3. Reliable Operation (Engineering) Limit: This is even higher than the previous two and represents the practical energy floor necessary for transistors to operate reliably and effectively in real-world applications. This limit accounts for additional factors like operational stability, error rates, and overall system durability under normal operating conditions. This is a function of the heat produced because of 1. and 2. and solving for that with reversible computing solves for this as well. This limit going to be reached within a few years and we are seeing the early signs of it with the plateauing of clock speeds at around 3Ghz.