Asian chip stocks sold off today, pushing South Korea's Kospi index 10% lower and Japan's Nikkei 4% in the red. That followed a tough session for U.S. chipmakers that looks set to extend to today, with Intel, Micron and others sliding premarket.

Here are some things weighing on investors' minds:

-- Chinese strides: A stratospheric stock-market debut by Chinese memory-chip maker CXMT, whose products Apple wants to use, highlighted growing competition for U.S. firms. An Information report that China has started making ultra-advanced chipmaking machines stoked fears the West could lose its stranglehold on a crucial component of the chip supply chain.

-- A possible megaproject: A Wall Street Journal report that Nvidia could provide a roughly $250 billion backstop for a massive OpenAI data-center project helped send shares in the chip giant down 5% yesterday, sparking concerns about the extent to which Nvidia is investing in its own customers.

-- Supercharged AI spending: Investors are skittish about other U.S. tech giants' heavy spending, too, with Microsoft, Meta, Apple and Amazon all due to report earnings later this week. "Those companies embody the critical theme weighing on sentiment in the markets right now," said Kyle Rodda, senior financial market analyst at online brokerage Capital.com. He says investor worry that excessive spending "will eat into returns."