Photo: S h y numis / Wikimedia Commons, CC BY 4.0, cropped
Korea's KOSPI Crashed 5.5% in a Day as SK Hynix Fell 10%. Is the AI Memory Boom Over?
- The KOSPI fell 5.46% to 6,035.35 on October 13, 2026. It briefly dropped below 6,000 during the day.
- SK Hynix fell 10.09% and Samsung Electronics fell 7.39%, the two biggest stocks in the index.
- Foreign investors sold a net 4.51 trillion won (about $3.35 billion) of Korean shares in one day.
- A sell-side 'sidecar' that pauses automated selling was triggered for the first time since August 19.
- The trigger: China's CXMT said it will unveil next-generation server DRAM within the year. The KOSPI has lost more than 1,000 points in five sessions from above 7,000.
What happened
South Korea's main stock index, the KOSPI, fell 5.46% on Tuesday, October 13, closing at 6,035.35. At its worst it dropped to 5,988, below the 6,000 mark.
It was the latest leg of a sharp slide. Five sessions earlier, the index was above 7,000.
The two stocks that did the damage
Korea's market is dominated by two companies that make memory chips, the parts that store data inside every AI server:
| Stock | Move on Oct. 13 | Close |
|---|---|---|
| SK Hynix | −10.09% | 1.44 million won |
| Samsung Electronics | −7.39% | 232,000 won |
| KOSPI index | −5.46% | 6,035.35 |
Source: Yonhap via Korea JoongAng Daily.
Foreign investors sold a net 4.51 trillion won, about $3.35 billion, in one day. The exchange triggered a sell-side sidecar, a five-minute pause on automated selling, for the first time since August 19.
Japan's Nikkei fell 1.8% the same day as memory and storage stocks slid across Asia.
The trigger: a Chinese rival
CXMT (ChangXin Memory Technologies), China's biggest memory chipmaker, said it will unveil next-generation server DRAM within the year.
That matters because server memory for AI is the most profitable thing Samsung and SK Hynix sell. Prices have soared because only a few companies can make it. A credible new supplier from China threatens those prices.
Add a sell-off in US chip stocks the night before and nerves ahead of US inflation data, and the selling snowballed.
The irony: record profits a week ago
Just last week, Samsung reported a record quarterly profit of about 107 trillion won, more than Nvidia. The companies are earning more than ever. Investors are worried about what happens to prices next year, not about this year's results.
The next day brought a different signal. ASML, which makes the machines chipmakers use to build factories, said customers want more equipment than it can supply through 2028. Demand for memory is still rising. The fight is over who gets paid for it.
Why it matters if you don't own Korean stocks
- US chip stocks moved first. Micron, Nvidia and other chipmakers fell the night before. Korea's crash and US chip moves feed off each other.
- Your index fund has exposure. Samsung is one of the largest stocks in emerging-market funds. Chip stocks are a big part of the S&P 500 and Nasdaq-100.
- Concentration cuts both ways. Korea's market rose fast because two stocks did. It fell fast for the same reason. We covered this in the KOSPI's two-stock problem.
What investors can do
Don't chase the bounce or the panic. Memory chips are the most cyclical part of tech. Prices swing from shortage to glut every few years. Our guide to memory chips explains the cycle.
Check how much chip exposure you already have. If you own an S&P 500 or Nasdaq-100 fund, you likely hold more semiconductors than you think. See how much AI you already own.
Stay diversified. A 5% drop in one country's market is a big headline but a small move in a globally diversified portfolio.
What to watch next
- CXMT's product launch and its pricing.
- Memory chip contract prices for the fourth quarter.
- Foreign selling. Whether it slows or keeps going will set the KOSPI's direction.
Frequently asked questions
Why did the KOSPI fall on October 13, 2026?
The KOSPI fell 5.46% mainly because memory chip giants SK Hynix and Samsung Electronics plunged after China's CXMT said it would unveil next-generation server DRAM within the year, raising fears of more competition. A sell-off in US chip stocks the night before and worries ahead of US inflation data added to the pressure.
How much did SK Hynix and Samsung stock fall?
SK Hynix fell 10.09% to 1.44 million won and Samsung Electronics fell 7.39% to 232,000 won on October 13, 2026, according to Yonhap-sourced reports.
What is a sidecar in the Korean stock market?
A sidecar is a five-minute pause on program (automated) trading orders that the Korea Exchange triggers when index futures move sharply. A sell-side sidecar was triggered on October 13 for the first time since August 19. It is milder than a circuit breaker, which halts all trading.
Who is CXMT?
ChangXin Memory Technologies is China's largest maker of DRAM memory chips. It has grown quickly with state support. Its plan to sell advanced server memory threatens the high prices that Samsung, SK Hynix and Micron have been charging AI data centres.
Is the AI memory boom over?
Not necessarily. Demand from AI data centres is still growing, and equipment maker ASML said on October 14 that its customers want more machines than it can build through 2028. The worry is about prices and profit margins as new competitors arrive, not about demand disappearing.
Primary sources
- Korea JoongAng Daily — Kospi plunges 5.5% as Samsung, SK hynix lead AI-driven tech sell-off (Oct. 13, 2026)
- KED Global — Kospi tumbles as chip rout deepens, briefly breaking below 6,000 (Oct. 13, 2026)
- The Herald Business — Kospi plunges below 6,000 intraday; sell-side sidecar triggered
- The Asia Business Daily — Samsung Electronics, SK hynix plunge 8%, 10%
- Seoul Economic Daily — KOSPI plunges, falls below 6,000 on memory supply fears
Data & disclaimer: This article is for educational purposes only and is not financial or investment advice. Figures reflect data available as of Oct 14, 2026, and conditions change — always confirm current pricing, rates and rules with the provider before you act. Written by Elizabeta Dimoska. See our editorial standards and disclosure.
Comments