Kospi's 11% Crash Sends Micron, AMD Tumbling in US Premarket

South Korea's Kospi plunged as much as 11% intraday on Tuesday, closing down 10.84% at 6,023.66, and the shockwave didn't stop at the Pacific — U.S. chip stocks were already sliding in premarket trading before Wall Street's opening bell.

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What happened in Seoul

The Kospi fell 732.09 points to 6,023.66, narrowly holding the 6,000 line after briefly breaking below it during the session. A level-1 circuit breaker was triggered at 10:13 a.m. local time, halting trading for 20 minutes as the sell-off accelerated. Samsung Electronics dropped 13.1% and SK Hynix fell 13.5%, according to the Associated Press, with the two chipmakers' heavy weighting in the index dragging the broader market down with them. Foreign investors were the main sellers, offloading a net 4.46 trillion won (roughly $3.2 billion), while individual retail investors bought 3.6 trillion won trying to catch the falling knife. As I covered in Kospi's Worst Day Ever: 10.84% Crash Shatters the 6,000 Line, this ranks as the second-largest single-day decline in the index's history, behind only June 23's drop.

Why it happened — and why it's spreading

The proximate trigger was a report that China has begun domestic production of deep ultraviolet (DUV) lithography tools, feeding fears that Chinese chipmakers are closing the gap on Western and Korean semiconductor equipment faster than expected — a theme I flagged in CXMT's Expansion and Nvidia's Financing Doubts Just Sank Kospi. Layered on top of that is a deeper worry: the Silicon Data LLM Token Expenditure Index, which tracks what companies actually pay per million AI tokens, is down nearly 20% from its May peak. A falling token price signals that AI users are migrating toward cheaper, often open-source models — which directly threatens the capex assumptions behind the massive buildout of GPUs, memory chips, and data centers that has powered the Nvidia-Samsung-SK Hynix trade for the past two years.

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Who's getting hit on Wall Street

The pain crossed straight into U.S. premarket trading. Micron Technology slid more than 5%, while AMD and Intel each dropped over 4%, according to Benzinga and TradingKey. Nvidia fell around 1.1%, and Applied Materials — a key supplier of chipmaking equipment — lost roughly 3.6%. Nasdaq 100 futures slid about 1.1% as of Tuesday morning, with S&P 500 futures down 0.3% and Dow futures roughly flat, underscoring how narrowly the damage is concentrated in semiconductors rather than the broader market.

The stocks most exposed are the ones most tied to the AI infrastructure buildout: memory makers like Micron who compete directly with Samsung and SK Hynix, equipment suppliers like Applied Materials whose order books depend on continued fab expansion, and GPU makers like Nvidia and AMD whose valuations assume token demand keeps climbing rather than shrinking.

What to watch next

Two catalysts converge this week. The Federal Reserve's July policy meeting began the same day as the Kospi crash, and any signal on rate policy will ripple through richly valued tech names already under pressure. Just as important is whether the Silicon Data Token Expenditure Index stabilizes or keeps sliding — a continued decline would reinforce the market's growing skepticism that AI infrastructure spending is outrunning actual usage, a dynamic Allianz researchers have compared to the gap seen during the 2001 telecom bubble. Traders will also be watching whether Samsung and SK Hynix stabilize when Korean markets reopen, since another leg down there would likely reignite the same premarket pressure on U.S. chip names.

This is not financial advice — always do your own research before making investment decisions.

The bigger picture: this isn't a China-specific scare or a one-day Korea problem — it's the market re-pricing how confident it is that AI token demand justifies the hundreds of billions being poured into chips and data centers. Until that Token Expenditure Index finds a floor, expect U.S. semiconductor names to keep trading as a proxy for Kospi's overnight moves.