I attended one of his talks (but not the ones you mention), during which he described how he was approaching the topic. He said he was reading the most important papers on sat problems in chronological order, and implementing each of the algorithms he found along the way. At the time of the talk, he was half-way through the ‘80s, IIRC.

A lesson in commitment and perseverance for me. And a very funny talk as well (Knuth likes jokes!)