Korea's KOSPI Jumped 6.6%, Then Fell 3.5%. How Seoul's Week Set Up the Chip Rout
SK hynix's record quarter lifted Korea's KOSPI 6.6% on Wednesday. Samsung's record didn't, and on Friday the index fell 3.5%, hours before New York's chip stocks sold off.
Part of the running storyAI Memory for 2027 Is Sold Out Before It's Made: What the Evidence SaysOn Friday, Korea’s KOSPI index fell 3.5%, Reuters reported, in a session that ended hours before New York opened. Later that day, the Philadelphia Semiconductor Index fell 7.2% in New York, NBC News and Reuters reported.
It ended a week in which Seoul’s two memory giants both reported record quarters. The first record lifted the market. The second didn’t, and by Friday Seoul had already sold the chip trade that New York sold next.
Wednesday: SK hynix’s record lifted Seoul and New York
SK hynix said on Wednesday that its quarterly revenue had topped 100 trillion won for the first time, and that it expects demand for memory to outrun supply through 2030, according to its results release (our story).
Seoul’s KOSPI jumped 6.63% and SK hynix rose 10.89%, the Korea Times reported.
New York followed the same day. Sandisk (SNDK) jumped 7.7% and Micron (MU) 5.9%, and the hard-drive makers Western Digital (WDC) and Seagate (STX) rose too.
Thursday: Samsung’s record wasn’t enough
On Thursday, Samsung reported a record third-quarter operating profit of 107.44 trillion won, about $80 billion, CNBC and the Korea JoongAng Daily reported. Nearly all of it came from its chip division.
The rest of the report disappointed. Revenue of 195.25 trillion won fell short of the 195.79 trillion won that LSEG SmartEstimates expected, CNBC reported, and the JoongAng said Samsung’s phone business swung to an operating loss as pricier memory chips raised its costs.
The headline wasn’t news, either. Samsung had flagged operating profit of about 107.4 trillion won in preliminary results on 8 October, TrendForce and ShareSansar reported. It also promised another 55 trillion to 75 trillion won of buybacks and dividends this year, but left the split to a board meeting in late January 2027.
Samsung’s shares fell 4.13% on Thursday, CNBC and the JoongAng reported, and the KOSPI gave up its morning gains to close down 1.24%, according to the JoongAng.
“Investors have been so spoilt by the AI trade that a record result is now treated as the bare minimum,” Josh Gilbert, APAC lead analyst at eToro, told CNBC. Anyone holding Samsung today, he said, “is really holding a memory maker with a phone business attached.”
Friday: Seoul sold first
Seoul trades while New York sleeps. Before Friday’s open in Seoul, Intel (INTC) had warned that a memory shortage was choking PC demand, and its shares had fallen 19.6% after hours on Thursday evening (our Intel recap).
The selling came early. The KOSPI was down 5.25% at 11:20 a.m. Seoul time, and a “sidecar” rule paused program trading for five minutes, Yonhap reported, citing renewed doubts about how long the AI boom can last.
The index closed down 3.5%, Reuters reported.
Samsung lost 3%, heading for its first monthly decline since July, according to Reuters, and SK hynix fell more than 7%, according to the Korea Herald and Invezz.
Later on Friday, New York followed. The Philadelphia Semiconductor Index fell 7.2%, and Intel plunged 28.6%, its worst day since 1974 (our market wrap).
What Seoul’s week told US investors
The SK hynix rally didn’t survive the week. Every one of these US chip stocks closed on Friday below where it stood on Tuesday, before SK hynix reported.
Sandisk shows the lesson Seoul taught first. It plunged 13.5% on Friday after beating estimates on Thursday evening (our story).
Its forecast still called for growth, just slower: sales about 12% higher this quarter, after a 23% jump in the last one. As with Samsung, a strong quarter wasn’t enough.
What moved prices all week was the outlook for AI spending, not the quarter just reported. SK hynix’s promise of a shortage through 2030 lifted memory stocks in both cities; Intel’s PC warning and worries about Big Tech’s spending took the gains back within two days.
Our read
We think Seoul’s week showed what the market now pays for: proof that the spending behind the records keeps growing, not the records themselves. Samsung’s 107 trillion won had been public for three weeks, and its stock fell; SK hynix’s record, with its forecast of a shortage through 2030, lifted the KOSPI 6.6% in a day. Seoul will trade on that question first, on Monday.
What’s next
- Monday, 2 November: Seoul’s first session since New York’s Friday selloff.
- Tuesday, 3 November: AMD (AMD) reports after the close (our preview).
- Wednesday, 4 November: Arm (ARM) and Qualcomm (QCOM) report. Last quarter, when Qualcomm’s phone-chip sales fell 20%, its chief executive pointed to “a challenging memory and supply environment” (the week ahead).
- Late January 2027: Samsung’s board decides how its extra shareholder payout splits between buybacks and dividends.
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Mostly Markets is for information and education only and isn't investment advice. Dev Malhotra is a pen name. Prices are from Nasdaq and CNBC as of the time stated.
