Key points
- Kospi closed Tuesday at 6,023.66, down 732.09 points or 10.84%, its fourth largest one-day fall on record. It traded as low as 5,992.91.
- Korea Exchange halted all Kospi trading for 20 minutes at 10:13 a.m. Seoul time, the eighth marketwide circuit breaker of 2026. Kosdaq got its own at 12:01 p.m. and closed down 7.72%.
- Samsung Electronics fell 13.39% and SK Hynix fell 14.65%. Japan's Nikkei 225 closed down 3.95%, with Kioxia down 18.33%.
- Foreign investors sold a net 4.9664 trillion won ($3.38B USD) of Kospi stock. Korean retail investors bought a net 4.3337 trillion won ($2.95B USD).
- The US carryover went into memory and storage. At 10:57 a.m. ET, Sandisk was down 14.52%, Western Digital 12.03%, Dell 11.49% and Micron 9.54%.
- Nvidia was a few cents above Monday's close at the same moment, and the Dow was up 0.81%. What got repriced is memory supply.
South Korea's Kospi closed Tuesday, July 28 at 6,023.66, down 732.09 points or 10.84%. That is the fourth largest one-day drop in the index's history, and the worst since March 4 of this year, when it fell a record 12.06%. It went as low as 5,992.91 during the day, under 6,000 for the first time since April 14.
Korea Exchange stopped trading in every Kospi stock for 20 minutes starting at 10:13:43 a.m. Seoul time, after the index had spent a full minute more than 8% below Monday's close. It was at 6,213.51, down 8.02%, when the halt fired. That was the eighth marketwide circuit breaker of 2026 and the 14th since Korea introduced the mechanism. The smaller Kosdaq index tripped its own at 12:01 p.m. and closed down 7.72% at 705.85.
Both markets had already hit sell-side sidecars in the first fifteen minutes, Kospi at 9:06 a.m. and Kosdaq at 9:14 a.m. A sidecar is the smaller brake, pausing program trading for five minutes when futures move far enough. A circuit breaker stops everything.
Two companies are more than half the index
Samsung Electronics closed down 13.39% at 220,000 won ($150 USD). SK Hynix closed down 14.65% at 1,550,000 won ($1,054 USD). Between them they carry more than half the Kospi's weight, so most of what happened to the index is just those two.
That concentration is why Seoul takes a memory headline harder than anywhere else does. The Kospi closed at a record 9,114.55 on June 22, after a run that had made it the best performing major market in the world this year. Tuesday's close is 33.9% below that record. The index ended June at 8,476.48, so it's down 28.9% in July alone.
Japan got a lighter version. The Nikkei 225 closed down 3.95% at 62,364.92, its lowest since May, and memory maker Kioxia fell 18.33% to 44,550 yen.
Two China headlines landed on the same day
Neither was about demand for AI chips. Both were about who gets to build them.
The first was ChangXin Memory Technologies. China's biggest DRAM maker listed on the Shanghai Stock Exchange's STAR Market on Monday and closed its first day up 465.82%, worth near $488 billion and about level with Intel. CXMT held 7.6% of the DRAM market in the first quarter, against 89.7% for Samsung, SK Hynix and Micron combined. What moved stocks wasn't the market share. It was the funding. A company with a state-backed balance sheet and an $8.6 billion IPO behind it can now add capacity into a market where the incumbents have been earning record margins on tight supply.
The second was lithography. The Information reported Monday that a state-backed Shanghai firm has begun building immersion deep ultraviolet machines, the tools that print circuits onto wafers, in an area where ASML has effectively no competition outside Japan. First deliveries are planned this year for SMIC, Hua Hong Semiconductor and CXMT. The volumes are tiny, near five systems this year and about 20 in 2027, against the 131 immersion DUV systems ASML shipped last year, and the machines still trail on performance. Traders read it as a signal about how long US export controls hold, not as a 2026 revenue problem.
Korean coverage added a third item, renewed worry about circular financing in AI, where a chip supplier helps underwrite its own customers' spending. Han Ji-young at Kiwoom Securities named the China competition issue and the circular investment issue together as the two things that could keep volatility high near term. Nvidia's reported talks to guarantee about $250 billion of OpenAI's data center financing had reached Seoul the day before.
Not everyone there thought the selling was proportionate. Kim Dong-won, head of research at KB Securities, argued that CXMT's capacity expansion may run for several more years without spreading into a broad oversupply across the whole DRAM market.
Korean retail bought nearly every share the foreigners sold
Foreign investors sold a net 4.9664 trillion won ($3.38B USD) of Kospi stock on Tuesday. Institutions bought a net 630 billion won ($429M USD). Korean individual investors bought a net 4.3337 trillion won ($2.95B USD). Korean outlets published slightly different totals depending on when in the afternoon they took the snapshot, and Korea Exchange settles the figures after the close.
Foreigners sold 2.9039 trillion won on Monday, and the two names they sold most were the same two. Retail investors have been the marginal buyer on the way down all month, which is one reason the Financial Services Commission is tightening deposit requirements on leveraged ETFs effective July 31.
The US selling sorted itself by what each company actually sells
Here is where US names stood at 10:57 a.m. ET Tuesday, against Monday's closing prices.
| Stock | Jul 27 close | 10:57 a.m. ET Jul 28 | Change |
|---|---|---|---|
| Sandisk (SNDK) | $1,278.23 | $1,092.65 | -14.52% |
| Western Digital (WDC) | $497.92 | $438.05 | -12.03% |
| Dell (DELL) | $426.91 | $377.87 | -11.49% |
| Seagate (STX) | $816.99 | $729.20 | -10.75% |
| Micron (MU) | $900.20 | $814.33 | -9.54% |
| Lam Research (LRCX) | $291.61 | $264.10 | -9.43% |
| AMD | $494.95 | $451.09 | -8.86% |
| Applied Materials (AMAT) | $516.89 | $473.92 | -8.31% |
| SK Hynix (SKHY) | $143.02 | $131.48 | -8.07% |
| Marvell (MRVL) | $189.17 | $174.02 | -8.01% |
| KLA (KLAC) | $203.36 | $189.30 | -6.91% |
| Intel (INTC) | $91.67 | $86.21 | -5.96% |
| ASML | $1,653.11 | $1,572.27 | -4.89% |
| Broadcom (AVGO) | $383.22 | $377.66 | -1.45% |
| Nvidia (NVDA) | $196.51 | $196.63 | +0.06% |
ASML's percentage is measured against a dividend-adjusted prior close. The other figures use unadjusted closing prices.
Nvidia sat a few cents above Monday's close while the memory makers, the drive makers and the equipment suppliers lost between 5% and 15%. That's the whole story of the day in one column. Neither China headline touched GPUs, and the market sorted the damage accordingly.
Dell is the odd name on that list, and its decline didn't start Tuesday. It fell about 14% on July 15 in the same AI hardware unwind. Dell buys memory rather than selling it, so cheaper DRAM eventually helps its margins. It doesn't help a stock that had tripled on AI server growth.
Everything on the list is also well off its opening lows. At 10:09 a.m. ET, before the bounce, Sandisk was down 15.76%, Dell 14.30% and Nvidia 1.16%.
The index level is understating all of this
At that same 10:57 reading, the SPDR Dow Jones Industrial Average ETF (DIA) was up 0.81% and the SPDR S&P 500 ETF (SPY) was flat. The Invesco QQQ Trust (QQQ) was down 1.32%, the VanEck Semiconductor ETF (SMH) down 3.95%, and the iShares MSCI South Korea ETF (EWY) down 5.26%.
A green Dow next to semiconductors down 4% is money leaving one trade, not a market in trouble. The same split showed up Monday, when chips erased a 1.7% overnight Nasdaq gain while the Dow held.
Korea has nowhere to rotate to. Its market has been force paused more times this year than in all of 2008, and the reason is the same one that made it the world's best performer through June.
Two events Wednesday decide the rest of the week
SK Hynix reports second quarter results Wednesday, July 29. Even the lowest analyst forecast on the sheet beats what the company earned in all of 2025. That quarter ended before any of this happened, so the guidance and the pricing commentary carry the weight, not the print.
The Federal Reserve announces its rate decision the same day at 2 p.m. ET, with Chair Kevin Warsh taking questions at 2:30. Traders had the odds of an increase at 38% as of July 24, against 10.7% on July 15. Microsoft (MSFT) and Meta (META) report after that close, and both are large buyers of the memory that just repriced.
Sources
- 이투데이 (Etoday), July 28, 2026, for the Kospi and Kosdaq closes, the Samsung and SK Hynix prices, net investor flows and the Kim Dong-won comment
- 파이낸셜뉴스 (Financial News) and 뉴스핌 (Newspim), July 28, 2026, for the sidecar and circuit breaker times and the Han Ji-young comment
- Live US market data at 10:57 a.m. ET on July 28, 2026, against July 27 closes. Won converted at 1,470.26 to the dollar
None of this is investment advice. US prices here are intraday and the session runs to 4 p.m. ET. Two of the three catalysts concern supply arriving in 2027 and later, and no company on that table has yet reported a quarter that reflects any of it.
