SK Hynix’s Record Run: Portfolio Constraints Clash with HBM4E Competition

SK Hynix shares surge fourfold to record 2,333,000 KRW, triggering mandatory liquidations by global funds. NPS buffers sell-off as Samsung races ahead with HBM4E samples.

The rally in SK Hynix shares has been nothing short of breathtaking — a fourfold surge since October 2025 that pushed the stock to a fresh 52-week high of 2,333,000 KRW on Friday. But beneath the surface of that milestone, two very different forces are pulling in opposite directions: mandatory portfolio liquidations by global fund managers and an intensifying race with Samsung over next-generation HBM memory.

On Thursday, the stock had already notched a new high of 2,320,000 Won before extending gains the next day. The relentless climb, however, has triggered automatic sell orders at several asset managers. Houses such as GAM Investment Management in Zurich and Jupiter Asset Management in Singapore have been forced to reduce their SK Hynix positions — not because of a loss of conviction, but because the stock’s weighting breached internal diversification limits. Many funds cap any single holding at 10% of the portfolio, while positions exceeding 5% together cannot represent more than 40% of total assets. The resulting mechanical selling has contributed to capital outflows from South Korean equities, according to market analysts.

A buffer has come from an unexpected source: the National Pension Service (NPS), South Korea’s sovereign wealth fund, which announced plans to raise its target allocation for domestic stocks. That signal on Friday helped absorb some of the liquidation pressure, keeping the broader KOSPI index from taking a heavier hit. Still, the concentration problem is stark — SK Hynix and Samsung Electronics together account for roughly half of the entire index, according to RBC, meaning any single-stock move ricochets directly into the benchmark.

Institutional investors unable to hold SK Hynix or Samsung directly are now hunting for proxies. They are turning to subsidiaries, holding companies, and insurers with large stakes in the chipmakers, preserving exposure to the AI supply chain without violating concentration rules. The structural demand for high-bandwidth memory continues to rise, fuelled by artificial intelligence infrastructure spending.

That demand backdrop makes the competitive picture particularly critical. Just as SK Hynix stocks hit their latest peak, Samsung announced it had shipped samples of its 12-layer HBM4E chips to key customers. The new memory modules boast speeds of up to 16 Gbps and a bandwidth of 3.6 TB/s per stack — more than 20% faster than the preceding HBM4 generation. Samsung’s timeline puts it ahead of SK Hynix, which plans to deliver its own HBM4E samples in the second half of 2026 and begin mass production in 2027. Sample shipment, however, is not the same as customer qualification or volume delivery, and Samsung still trails in market share.

According to Counterpoint Research, SK Hynix commanded 57% of the global HBM market in the fourth quarter of 2025, versus Samsung’s 22% and Micron’s 21%. The leader’s financial strength is reflected in its first-quarter 2026 results: revenue of roughly 52.6 trillion Won and an operating margin of 72%. Those numbers underscore how tightly the business remains tied to scarce AI memory supply. The real risk for SK Hynix is not the current quarter’s performance, but whether it can carry its pricing power into the HBM4E cycle.

With the stock up about 243% year-to-date, the market is already pricing in a strong continuation. Samsung’s early sample push sets a visible benchmark. Whether SK Hynix can match or exceed its rival on bandwidth, energy efficiency, and thermal management in its own HBM4E samples will determine who dictates volumes and prices in the next acceleration cycle. For now, the company is navigating a two-front battle: managing the mechanical constraints of portfolio rules at home, while fending off a resurgent competitor abroad.