South Korean stocks jump 6.63% after SK Hynix earnings revive AI optimism

The AI spending boom delivered profits, not just promises, for SK Hynix—and investors rewarded it. South Korea’s KOSPI closed 6.63% higher on October 28 after the memory-chip maker reported record quarterly earnings and a large shareholder-return program. The rally offered reassurance about AI demand while triggering a temporary curb on automated buying.

SK Hynix reported record third-quarter revenue and operating profit, supported by strong demand for memory chips used in AI applications. Operating profit increased 631% from a year earlier, according to Investing.com’s account published by Yahoo Finance. The results put a sharp rise in earnings behind the enthusiasm for AI-linked chipmakers.

Alongside those results, the company announced a shareholder-return program worth more than 100 trillion won, or $75.3 billion, for 2026. That announcement gave investors a second reason to buy: the company paired its record earnings with a commitment to return money to shareholders.

Yuanta Securities analyst Lee Jae-won said the combination showed that strong AI-chip demand could translate into operating profits and shareholder returns. In Yonhap’s coverage carried by UPI, he argued that the results eased concerns about the sustainability of the AI-driven rally and a possible peak in the memory-chip cycle.

+10.89%SK Hynix

SK Hynix finished at 1.49 million won after leading the earnings-driven chip rally.

+9.01%Samsung Electronics

Samsung Electronics also advanced sharply, closing at 242,000 won.

Buying trips a five-minute trading curb

The benchmark KOSPI added 374.1 points to finish at 6,012.44, after reaching 6,032.28 during the session. The closing figures extended an early rally that had already lifted the index more than 6% and brought it to its highest level in two weeks.

Shortly before 11 a.m., the Korea Exchange activated a buy-side sidecar—a temporary restriction on program trading. It suspended program-trading buy orders for KOSPI-listed stocks for five minutes. The restriction applied to those automated buy orders, rather than stopping all trading in the market.

The mechanism is triggered when KOSPI 200 futures rise at least 5% and remain at that level for at least one minute. Wednesday marked its activation for a second consecutive session, making the trading curb another measure of the speed of buying.

Foreign buyers join institutions

The gains reached beyond the two biggest chipmakers. SK Square rose 11.23%, while Samsung Electro-Mechanics gained 8.74%. Across the market, advancing shares outnumbered declining shares 580 to 288. Turnover totaled 223.2 million shares worth 19.83 trillion won, although Yonhap described trading volume as light.

Foreign investors bought a net 815.83 billion won of shares, and institutions bought a net 960.79 billion won. Individual investors moved in the opposite direction, selling a net 1.8 trillion won. The session therefore combined broad price gains with a clear split between those investor groups.

Attention next turns to Alphabet and Microsoft, scheduled to report after the U.S. market close. Investors are looking for evidence that heavy AI-infrastructure spending is producing durable revenue growth. That is a different test from the strong profits already reported by a supplier of the memory chips used in AI systems.

The Federal Reserve’s rate decision was also due later Wednesday in the United States, or early Thursday in South Korea. Rates were widely expected to remain unchanged, with investors watching policymakers’ guidance for signals about the future path of borrowing costs.