SK Hynix's 8% Rout Triggers Second Circuit Breaker as DDR5 Pivot Sours AI Premium
27.06.2026 - 18:07:40 | boerse-global.de
Seoul’s main board ground to a halt for the second time in five trading sessions on Friday as SK Hynix shares crashed 8.36% in a single day, wiping out the prior session’s record high. The Korea Exchange suspended trading on the KOSPI for 20 minutes after the benchmark slid more than 8% intraday, with selling concentrated in the very semiconductor names that had powered the market’s recent surge. It marked the first time since the exchange’s founding that circuit breakers were activated twice within a single week.
The trigger for the violent reversal was not a demand shock but a strategic production shift. SK Hynix, the world’s dominant supplier of high-bandwidth memory (HBM), plans to convert a factory originally slated for HBM4 output to standard DDR5 DRAM. The move is driven by near-term economics: DDR5 prices are rising amid tight supply, and margins on that commodity-grade memory currently look more attractive than the still-ramping HBM4 segment. Crucially, this does not represent an exit from the AI chip business — the company remains the lead HBM supplier to Nvidia, with whom it signed a multi-year technology partnership just last month covering memory for Nvidia’s Vera-Rubin platform. But the market read the recalibration as an early sign that the premium investors have assigned to SK Hynix’s AI credentials may be less durable than hoped.
Just three days earlier, SK Hynix had dethroned Samsung Electronics as South Korea’s most valuable listed company, with a market capitalisation of 2,080 trillion won against Samsung’s 2,067 trillion won. The ascent had been fuelled by relentless demand for HBM, the specialised chips that accelerate artificial intelligence workloads. That same concentration — and the resulting crowded positioning — made the stock acutely vulnerable when the DDR5 news landed. By Friday’s close, the shares had sunk to 2,673,000 KRW, a 10.5% retreat from the 52-week high of 2,987,000 KRW touched on June 25. Over the full week, SK Hynix lost 3.29%.
Should investors sell immediately? Or is it worth buying SK Hynix?
Despite the rout, the technical backdrop remains far from broken. The stock still sits nearly 40% above its 50-day moving average of around 1,911,000 KRW, and the year-to-date gain stands at a staggering 295%. The 14-day relative strength index has fallen to 59.7, exiting overbought territory but hardly signalling a panic. What does give pause is the 30-day annualised volatility of 108% — a number that explains why the shares can swing violently even in the absence of fresh corporate news.
Whether Friday’s close proves to be a floor hinges on how the market interprets the DDR5 pivot in the coming days. If investors view the shift as a margin-maximising tactic rather than a retreat from HBM leadership, the stock could stabilise above the 2,600,000 KRW level. Should selling pressure persist, the question of how much of SK Hynix’s AI premium is derived from hype — and how much from sustainable earnings — will move back to centre stage. Either way, the events of the past week have served as a stark reminder that even the most dominant players in the AI infrastructure trade are not immune to the law of gravity.
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