Nvidia Corp. tumbled 3.5% on Aug. 19, its sharpest single-day fall since April 21, extending a two-week slide that has dented confidence in the market’s artificial-intelligence winners. The drop in the world’s most valuable chipmaker weighed on peers such as Advanced Micro Devices and Micron Technology and added to pressure on the broader technology complex. The tech retreat left the Nasdaq Composite down 0.67% and the S&P 500 0.24% at Wednesday’s close, while the Dow Jones Industrial Average finished virtually flat at 44,938.31. Semiconductor names and other megacap growth stocks were among the biggest laggards, erasing part of the gains notched since the spring rally. Risk appetite weakened further on Thursday morning after Walmart Inc. reported a rare profit miss and the Labor Department said initial jobless claims climbed to their highest level since June. U.S. equity futures slipped and chip shares remained under pressure in pre-market trading. Traders are bracing for Federal Reserve Chair Jerome Powell’s appearance at the Jackson Hole symposium on Friday for signals on whether policymakers are prepared to begin cutting rates as soon as September. Minutes of the central bank’s latest meeting showed growing dissent, adding to uncertainty around the policy outlook.