Korean stocks staged a sharp intraday reversal on October 1 as Micron’s earnings beat and news that 2026 HBM supply is sold out sent semiconductor names surging. KOSPI closed up 1.95% at 6,971.35; KOSDAQ soared 4.48%.
The KOSPI touched 7,171 on a US chip rally, then surrendered nearly all of it as retail investors dumped 1.6 trillion won. PCB makers jumped up to 29%, SK hynix fell, and the won strengthened to around 1,360 per dollar.
Micron’s fiscal quarters end in August, November, February and May, so it reports real DRAM/NAND numbers weeks before Samsung Electronics and SK Hynix. Here is how to read its bit-shipment guidance, HBM commentary, inventory days and capex as direct inputs into the next morning’s Samsung Electronics and SK Hynix open in Seoul.
The KOSPI closed above 7,000 for the first time in about two months, up 1.40%, as OpenAI’s GPT-6 launch lifted chip sentiment and battery materials rallied. Individuals sold a hefty 2.5 trillion won while institutions bought.
Korea’s KOSPI jumped 4.61% to 6,995.39 as OpenAI ‘Astra’ expectations powered Samsung Electronics and SK Hynix. Foreigners and institutions bought heavily while retail investors sold a near-record 8.26 trillion won.
The KOSPI sank 3.99% to 6,562.72 as US-Iran clashes near the Strait of Hormuz pushed Brent above $90 and US yields hit multi-month highs. Samsung Electronics and SK hynix fell over 4%, while biotech names surged to Korea’s 30% daily limit.
KOSPI reversed a 1.28% intraday drop to close up 0.23% as Samsung Electronics and SK Hynix extended their buyback-driven rally amid renewed US-Iran tensions. KOSDAQ fell 1.56% with all ten of its largest stocks lower; retail investors bought while foreigners and institutions sold.
The KOSPI opened down 2.6% and fell over 3% intraday before Samsung Electronics and SK hynix buybacks soaked up foreign and passive selling, lifting the index to close up 0.46% at 6,820. The KOSDAQ lagged as battery names slid.
Korean chip stocks can fall the morning after an Nvidia beat because the move was pre-positioned: the reaction runs through the after-hours print, guidance, overnight US futures and after-hours moves in other chip names before the 09:00 Seoul open. Here is the full transmission chain, with a worked example reading real August 2026 foreign-flow data into a purely hypothetical earnings night — heavy selling that fades to near flat, a de-risking backdrop whose post-result implications can cut more than one way.
The KOSPI plunged as much as 4.3% on overnight US chip weakness before Samsung Electronics and SK Hynix powered an afternoon reversal, closing up 0.68% at 6,742.74. Foreign investors sold heavily into the dip while retail bought. Nvidia’s earnings loom Wednesday.