U.S. stocks finished mixed Tuesday, Sept. 23, as the Nasdaq 100 rose 0.8% to a record close of 30,732 on renewed enthusiasm for artificial-intelligence infrastructure and chipmakers. Nvidia gained 0.7%, Micron rose 5% and Sandisk jumped 6.8% after a Rosenblatt upgrade, while Applied Materials added 1.8%. The S&P 500 closed flat after recovering from earlier losses, and the Dow added 185 points, although bank stocks including JPMorgan and Bank of America declined. Investors also monitored Treasury yields, oil and developments involving the United States, Iran and China.