US stocks today: S&P 500 ends down as AI worries hit chipmakers

US markets closed lower with the S&P 500 down 0.45 percent at 7,503.36 and Nasdaq falling 1.19 percent to 25,811.10, led by a selloff in chip stocks. Memory chipmakers Micron and Sandisk declined on concerns about stretched AI-linked valuations, while reports that Chinese startup DeepSeek is developing its own AI chip added to fears of reduced dependence on Nvidia. Investors also looked ahead to the Fed minutes release and South Korean giant SK Hynix listing debut on the Nasdaq.