Chip stocks tumbled across Asia and the US on Tuesday as investors questioned whether the billions flowing into AI infrastructure will ever earn a proper return, knocking Nvidia from its perch as the world's most valuable company.

The Korean circuit breaker

South Korea's Kospi index triggered a circuit breaker after sliding 8% in early trading, then fell another 3% after the halt lifted to close down 10.8%. Samsung Electronics and SK Hynix led the rout, each dropping more than 13%. The index had more than doubled from January to mid-June before surrendering roughly a third of its value, a swing amplified by heavy retail participation and widespread margin borrowing that exaggerates every downdraft.

The trigger and the crown

The immediate catalyst was a Wall Street Journal report that Nvidia is in talks to commit around $250 billion to an OpenAI data-center project. Nvidia shares fell 5% in New York on Monday, ceding the top market-cap spot to Apple, which has risen about 25% this year. SK Hynix's US-listed shares slipped 7.5% below its $149 Nasdaq debut price from July 9, while Japan's Nikkei 225 shed nearly 4%.

Profit-taking or paradigm shift

Not everyone sees a bubble bursting. Jane Sydenham of Rathbones frames the slide as a correction after "phenomenal rises," noting the Korean market's extreme concentration in two names. Jun Bei Liu of Ten Cap argues investors are merely taking profit ahead of the US holiday season and will likely return, though she flags rising Chinese competition as a structural worry. Cheng Chye Hsern of Providend suggests Apple's relative absence from the AI arms race is precisely what makes it a haven.

China arrives, Europe yawns

That competition arrived on cue Monday when ChangXin Memory Technologies surged 470% on its Shanghai debut, raising capital to expand DRAM production for AI servers and consumer devices. Meanwhile, European benchmarks, the FTSE 100, CAC 40, and DAX, shrugged off the panic, each rising about 0.6% on limited AI exposure. The divergence underscores a market increasingly split between those pricing in an AI revolution and those pricing in the bill.

What to watch next

Whether Nvidia's $250 billion conversation materializes into a term sheet, how quickly Korean retail margin calls stabilize, and if CXMT's debut marks the start of a Chinese memory supply response that could compress margins for Samsung and SK Hynix. The AI trade isn't dead, but the easy money has been made.