Kurzweil has an example of a task with 43,000x speedup over some period, more than Moore's Law, that is often mentioned in these discussions, and might be what you're thinking of. It was for one very narrow task, cherrypicked from a paper as the one with by far the greatest improvement. It's an extremely unrepresentative sample selected for rhetorical effect. Just as Kurzweil resolves ambiguity overwhelmingly in his favor in evaluating his predictions, he selects the most extreme anecdotes he can find. On the other hand, in computer chess and go software progress seems to have been on the same order as Moore's law too.

ETA: there were still improvements of many thousandfold over the period considering the rest of the paper.

Here is just one example, provided by Professor Martin Grötschel of Konrad-Zuse-Zentrum für Informationstechnik Berlin. Grötschel, an expert in optimization, observes that a benchmark production planning model solved using linear programming would have taken 82 years to solve in 1988, using the computers and the linear programming algorithms of the day. Fifteen years later—in 2003—this same model could be solved in roughly one minute, an improvement by a factor of roughly 43 million. Of this, a factor of roughly 1,000 was due to increased processor speed, whereas a factor of roughly 43,000 was due to improvements in algorithms! Grötschel also cites an algorithmic improvement of roughly 30,000 for mixed integer programming between 1991 and 2008. The design and analysis of algorithms, and the study of the inherent computational complexity of problems, are fundamental subfields of computer science."