SK Hynix Fell 10.1% and Samsung 7.4% on Korea's "Black Tuesday" — the Same Day China's CXMT Said a Denser Server DRAM Is Due by End-2026, With No Specs or Launch Date

On Tuesday, Oct 13, 2026, SK Hynix closed down 10.1% at ₩1,443,000 and Samsung Electronics down 7.4% at ₩232,000 on the Korea Exchange, while the KOSPI fell 5.5% to 6,035 and foreign investors sold a net of about ₩4.5 trillion of Korean stocks. Over two sessions SK Hynix is down about 15% from its Oct 8 close. The same day, China's CXMT said it plans to launch server DDR5 memory on a denser 4F² cell design by the end of 2026; it gave no detailed specifications and no launch date, and SK Hynix itself put a 4F² design on its own roadmap in 2025. Rising US long-term Treasury yields and heavy foreign selling were also on the record that day. No single cause explains the fall.