Microsoft is a major player in AI through its partnership with OpenAI and its Azure Cloud infrastructure. Citadel sold much of its Microsoft shares earlier this year, amid broader shifts in its investing strategy.

Interestingly, while Nvidia (NASDAQ: NVDA) and Taiwan Semiconductor (NYSE: TSM) are both positioned to benefit from demand for artificial intelligence (AI) infrastructure, Griffin bought one stock and sold the other in the third quarter.

Citadel Advisors, run by billionaire investor Ken Griffin, is one of the most prestigious hedge funds on Wall Street, and while reviewing the 13F it filed on Nov. 14, I noticed something. In the third quarter, the fund increased its stake by 172% in a semiconductor stock that isn't Nvidia.