We're closer than this to universal limits on computation, if it's not reversible computing.
With non-reversible computing, flipping a single bit, as you say, costs energy. There's a
minimum energy it MUST cost, dependant on operating-temperature.
So, how much can a laptop do if it's only allowed to consume 10W, operate non-reversibly, and
operate at room-temperature ? I did the math for rec.arts.sf.science some time back, and may
very well have done it wrong. But I got as a result that we're only ~5 OOM away from the
theoretical limits.