Chip stocks and AI names tumbled for a second day on Wednesday, as anxiousness rises ahead of Powell's Friday speech.

A wobble in U.S. technology shares has raised the stakes for Nvidia Corp's quarterly results on Wednesday, with earnings from the semiconductor giant posing a crucial test for the scorching AI trade.

Nvidia stock was falling early Friday. The chip maker looks to be facing serious obstacles to resuming sales of its artificial-intelligence processors in China. The shares were down 1% at $173.29 in premarket trading after rising 0.

Stocks opened lower Thursday, under pressure after a larger-than-expected rise in first-time unemployment claims and disappointing results from Walmart that saw the retail behemoth and Dow component miss Wall Street profit expectations.

The key metric of comparable sales for Walmart in the U.S. ticked up 4.6% year over year, meaning overall sales growth is largely organic and not just driven by opening new stores. While some investors were spooked,

Adjusted earnings per share were softer than Wall Street was projecting, coming in at 68 cents a share, compared with estimates for 73 cents. The adjusted figure excludes one-time gains on equity and other investments,