By Noel Randewich and Joel Jose, Reuterschip index tumbles more than 4 percent as investors worry about AI spendingApple rebounds from Thursday selloff S&P 500 +0.10 percent, Nasdaq +0.03 percent, Dow -0.02 percentWall Street was mixed on Friday, with gains in Moderna and other healthcare stocks, while AI-related chip stocks tumbled from recent highs.The Nasdaq was on pace for a more than 4 percent drop for the week and the S&P 500 was set for a fall of over 1 percent as high-flying semiconductor companies remained under pressure despite strong earnings from Micron Technology.Apple rose 1.5 percent, rebounding partly from a selloff on Thursday, when it raised iPad and MacBook prices, blaming soaring memory and storage chip costs.Moderna surged 13 percent to its highest level since 2024 after the drug developer hosted an investor event and showcased its pipeline.The S&P 500 healthcare index rose 2.5 percent, leading gains among the 11 sector indexes.The PHLX chip index sank more than 4 percent, underscoring recent volatility among AI-related chipmakers that have fuelled much of Wall Street's gains in recent years. While some investors remain optimistic about the potential for AI to fuel higher profits, others worry that massive spending to build AI data centres may take too long to pay off."It's too early to conclude that there's a major correction brewing in tech, but what I would say is that the questions around profitability and the capex story are certainly not going away," said David Stubbs, chief investment strategist at AlphaCore Wealth Advisory.Stubbs also warned that Wall Street could be vulnerable to signs that US companies may not be able to deliver on investors' high earnings expectations. US inflation rose above 4 percent in May, data showed on Thursday, as the Iran war drove up energy prices, keeping alive the possibility of a Fed rate hike.While oil prices have retreated sharply as Middle East tensions eased, Apple's newly announced price hikes suggest inflation remains a concern, said Art Hogan, chief market strategist at B. Riley Wealth."We saw a similar dynamic during the pandemic, when supply chain disruptions limited access to semiconductors. Now, we're witnessing a comparable supply shock, this time driven by memory, which is creating renewed inflationary pressure," Hogan said.The S&P 500 was up 0.1 percent at 7365 points.The Nasdaq gained 0.03 percent to 25,366.14 points, while the Dow Jones Industrial Average was down 0.02 percent at 51,909.81 points. A report that OpenAI was considering delaying its public debut until next year also weighed on risk sentiment toward the tech space. Shares of SpaceX were up 1.7 percent, and trading volume could be heavy before the session ends as passively managed index funds buy the stock ahead of its inclusion in Russell indexes.Meanwhile, interest rate concerns persisted, with traders pricing in one 25-basis-point rate hike and a near 27 percent chance of another by year-end, according to LSEG-compiled data.A survey showed US consumer sentiment rebounded from record lows in June, though households remained worried about the high cost of living.ON Semiconductor dropped 24 percent after agreeing to acquire Synaptics in an all-stock deal valued at about US$7 billion (NZ$12.4b). Synaptics shares were near flat.Advancing issues outnumbered falling ones within the S&P 500 by a 1.7-to-one ratio.The S&P 500 posted 28 new highs and five new lows; the Nasdaq recorded 191 new highs and 138 new lows.- Reuters