Stock market news today: S&P 500, Nasdaq futures tumble as China curb risk rattles techs Yahoo FinanceUS Floats Idea of Tougher Trade Rules in Chip Crackdown on China BloombergS&P 500 futures fall nearly 1% as investors continue to dump tech winners like Nvidia: Live updates CNBCDow Jones Futures Fall As Nvidia, Tesla, TSMC Tumble; ASML Dives On Earnings Investor’s Business DailyChina and Taiwan concerns hit chip stocks including Nvidia MarketWatch