Samsung and SK Hynix Rallied in Seoul on GPT-6 Astra, and…

Memory inventories at Samsung Electronics and SK Hynix have fallen below 10 days of supply, KB Securities disclosed on 7 September, as OpenAI's GPT-6 Astra launch reignited investor conviction that AI-driven demand for high-bandwidth memory will outlast the current chip cycle. The Kospi closed up 4.61% at 6,995.39, just 4.61 points short of the 7,000 mark.

Seoul's Chip Rally in Numbers

SK Hynix surged 8.26% to 1,783,000 won in Seoul on 7 September, extending an 8.1% advance in its US-listed ADR on Friday, 4 September, the last US session before the Labor Day holiday, and Samsung Electronics rose 5.68% to 270,000 won. Foreign investors net-purchased 2.59 trillion won ($1.93 billion) of Korean equities on the day, while institutional buyers added another 2.63 trillion won, according to the Korea Times. Retail investors were net sellers of 6.82 trillion won.The Kosdaq climbed 1.07% to 822.19, and the won strengthened 9.9 to 1,340.5 per dollar, its firmest level in 23 months. Across Asia, the Nikkei 225 gained roughly 2% to trade above 66,300, with the Topix up 0.55% at 4,125.80. The Hang Seng slipped about 1%, the CSI 300 added 0.59% to 4,575.02, and the ASX 200 closed near flat. The divergence underscored that the rally was led by AI-exposed semiconductor names rather than driven by broad risk appetite.

Why KB Securities Sees the Tightest Supply in History

Kim Dong-won, head of research at KB Securities, wrote that "the possibility that sellable memory volumes will be exhausted next year could become a reality," forecasting the tightest supply conditions in history for 2027. KB estimates that global hyperscaler AI infrastructure spending will reach $1.3 trillion in 2027, a 60% year-over-year increase. Memory's share of that spending is projected to climb from 14% in 2025 to 40% in 2026 and 57% in 2027, according to KB Securities' estimates, driven by HBM4 chips that require roughly three times the wafer capacity of conventional DRAM. Bit-based demand growth for DRAM and NAND is expected to exceed supply by more than 10 percentage points next year, with the squeeze hitting HBM, server DDR5, and enterprise SSDs simultaneously. Both Samsung and SK Hynix trade at roughly 3x Nomura's 2027 earnings forecasts, about 37% below their recent peaks, a market pricing cyclical decline rather than a structural shortage, Nomura analysts wrote in a 4 September note.

Astra Gave Investors a Reason to Reprice the Shortage

OpenAI unveiled GPT-6 Astra on 3 September. NVIDIA CEO Jensen Huang wrote on X that Astra was "trained on ~100K+ NVIDIA Grace Blackwell NVLink72" systems and that "400K GPUs coming online next." Huang added that "AGI has arrived", echoing OpenAI president Greg Brockman, who had opened the GPT-6 Astra press call on 3 September with "Welcome to the AGI era," telling reporters he believed OpenAI had reached AGI while acknowledging it remains "a gray, fuzzy thing" without an agreed definition, Axios reported.Kiwoom Securities analyst Han Ji-young noted that Astra "restored focus on AI demand momentum," while Meritz Securities' Hwang Soo-wook argued that "lower token prices should not automatically be read as weaker hardware demand." DB Securities analyst Seungyeon Seo raised SK Hynix's price target to 2.3 million won from 2 million won, with consensus targets implying more than 50% upside from current levels.

Micron Stands to Benefit From the Same Squeeze

The inventory squeeze is not limited to Korean producers. Micron (MU) faces the same supply arithmetic as HBM4 production cannibalises conventional DRAM wafer capacity across the industry. GPT-6 Astra did not create the memory shortage, but it gave the market a reason to believe the shortage lasts longer, and 7 September's Seoul tape is the first measure of how much longer investors are willing to price.KB Securities' sub-10-day inventory reading is a broker estimate, not a company disclosure, and the shortage thesis depends on hyperscaler capex plans holding at $1.3 trillion through 2027. Investors watching SK Hynix and Samsung should track HBM4 wafer allocation announcements and quarterly inventory disclosures rather than single-day price moves. The 37% drawdown from recent peaks and roughly 3x 2027 P/E ratios reflect how far the market has already repriced these names on cycle fears.