(Bloomberg) -- The artificial intelligence furor gripping the stock market has the shares of chipmakers like Nvidia Corp. soaring, making them increasingly crucial to the broader S&P 500 Index rally. But the stocks are no longer cheap, adding a new level risk to further gains in the broad equities benchmark.Most Read from BloombergTrump’s Net Worth Hits $6.5 Billion, Making Him One of World’s 500 Richest PeopleBiden Gains Ground Against Trump in Six Key States, Poll ShowsTrump Vows to Pay Fraud