Nvidia boosts tech stocks but caution dominates ahead of Fed speech

Blockbuster earnings from AI chip behemoth Nvidia boosted technology stocks Thursday, but broader market movements were muted as investors eyed a key speech by the US Federal Reserve chairman on the prospects for the world's biggest economy.In its highly anticipated report, Nvidia -- the world's biggest company by market value -- shattered analyst forecasts by unveiling revenues that more than doubled in the second quarter from the year earlier, to a whopping $96 billion.