SK Hynix Hits Its First-Ever 30% Limit-Up as Samsung Jumps 26%

SK Hynix slammed into its daily 30% trading limit on Thursday, July 31, touching 1,718,000 won and marking the first time the stock has hit a price limit since 2009 — and the first time ever under South Korea's current 30% price-band system. Samsung Electronics wasn't far behind, surging as much as 26-28% to a high of 261,500 won, while the Kospi index posted its largest single-day gain on record, up 17.9% to close at 6,695.45.

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What happened

The move was broad and violent. SK Hynix's 29.95% intraday spike pinned it at the exchange's maximum allowable daily gain, a threshold last touched under the old 15% band regime in 2009 when it traded as Hynix Semiconductor. Samsung Electro-Mechanics also hit limit-up, and Samsung Electronics — Korea's most heavily weighted stock — added roughly a quarter of its value in a single session. Foreign investors piled in aggressively, net-buying an estimated 5 trillion won ($3.6 billion) worth of Korean shares on the day, according to Money Today.

This wasn't an isolated Kospi spike either. As I covered in SK Hynix Nears Limit-Up as Kospi Rockets 17%, a Record Intraday Gain, the index was already flirting with the limit earlier in the session — Thursday's close confirms the stock actually got there, something the intraday numbers hadn't yet locked in.

Why it matters

The rally traces back to Wall Street. Microsoft's Azure cloud unit posted 43% growth with notably leaner AI infrastructure spending, easing fears that hyperscaler capex was about to crater — a theme I broke down in Microsoft's $485 Billion Day Sparks a 2.8% Nasdaq Rally. That reassurance rippled straight into Korean memory-chip stocks, which had been hammered over the prior week on fears that AI-driven demand was overextended and that leveraged positions were unwinding messily.

According to TradingKey's coverage of the session, analysts framed Thursday's move as a combination of three forces: renewed confidence that the deleveraging process was largely finished, oversold prices after the prior sell-off made shares look cheap again, and the same AI-buildout optimism now feeding U.S. tech names. That's a sharp reversal from the mood just days earlier, when I wrote about Kospi Soars 14%, Triggers Circuit Breaker on Chip Rebound — this week has effectively delivered two record-setting rebound days in the same stretch.

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Who's affected

SK Hynix and Samsung Electronics are the direct epicenter, given they make up an outsized share of Kospi market cap and are the world's two largest memory-chip producers. The rally also had a personal dimension: SK Group Chairman Chey Tae-won bought SK Hynix shares for the first time ever this week, a move Bloomberg tied directly to the stock's surge in its report, SK Hynix Shares Surge in Seoul on US Peer Rally, Chey Purchase. I covered that purchase in detail in Chey Tae-won Buys SK Hynix Stock for the First Time Ever, and it's clearly still resonating with investors days later.

Beyond the two chip giants, Samsung Electro-Mechanics' limit-up shows the buying pressure spread into the broader Samsung supply chain. U.S.-listed memory peer Micron is also in the crosshairs of this story, though its own trajectory has been rockier — as I noted in Micron's Down 31%. History Says the Drawdown Isn't Over Yet, Micron's drawdown hasn't mirrored the Korean rebound, underscoring that this move is concentrated in Korea for now rather than lifting every memory name equally.

What to watch next

Not everyone is convinced the bounce sticks. Invezz flagged in its report, SK Hynix soars 28%, Samsung 25%, but here's why this rebound may not last, that the same volatility driving shares up 20-30% in a day can just as easily reverse if AI-capex sentiment on Wall Street sours again. Watch three things in the coming sessions: whether foreign inflows into Korean equities persist beyond Thursday's 5 trillion won burst, whether U.S. hyperscaler earnings continue to confirm resilient AI infrastructure spending, and whether SK Hynix and Samsung can hold these levels without another sharp pullback like the one that preceded this rebound.

This is not financial advice — always do your own research before making investment decisions.

Thursday's session was historic by any measure — a first-ever 30% limit-up for SK Hynix, a record Kospi gain, and a Samsung surge that erased much of the prior week's losses in a single day. But the same forces that made the drop violent — leverage, concentrated positioning in a handful of chip names, and sentiment tied tightly to U.S. hyperscaler earnings — are still in play, which means the path from here is far from a straight line up.