Memory Selloff Hits Wall Street: Chip Index Falls 4.3%, Samsung and SK Hynix Down More Than 6% Before Seoul Open

Since CXMT president Cao Kanyu announced over the weekend before Monday, Oct. 12 that the Chinese memory maker plans to roll out a 4F² DRAM structure by the end of 2026, the selloff in memory stocks has widened from South Korea to Wall Street. The latest leg came on Wednesday, Oct. 14.

U.S. chip stocks take the hit

The Philadelphia Semiconductor Index dropped 4.3% on Oct. 14. The Nasdaq Composite fell 1.88%. Sandisk lost 5.97% and Micron 3.88%.

The damage was not limited to memory. AI cloud company CoreWeave plunged 15.46% as its debt load from data-center expansion came into focus.

Inflation added to the pressure. The September consumer price index rose 3.7% from a year earlier, above the 3.6% market forecast, which kept the risk of more Federal Reserve rate hikes on the table.

SK Hynix's Nasdaq-listed shares (SKHY) were down 3.41% in early trading Wednesday, in the mid-$150s. They had closed near $195 on Oct. 2 and Oct. 5.

Seoul gets the message early

Samsung Electronics and SK Hynix each fell more than 6% in Nextrade's premarket session early Thursday, Oct. 15 local time. That session runs 8:00 to 8:50 a.m. before the Korea Exchange's regular open.

The drop appeared to reflect the U.S. chip rout, concerns over the debt burdens of AI companies and the risk of additional rate hikes. The two companies supply high-bandwidth memory (HBM) for AI servers, plus server DRAM and storage. A delay in data-center spending would hit orders and shipments for all three.

This follows a difficult week in Seoul. SK Hynix and Samsung had already fallen 15% and 13% respectively since Monday's open in Korea, according to Morningstar's Tuesday tally.

What the competition argument says

Morningstar equity analyst Jing Jie Yu said CXMT's announcement disrupted investors' expectations around development timelines. "If the company can commercialize this technology ahead of its peers, it speaks volumes to China's DRAM technological competitiveness and raises risks of oversupply longer term," he said.

ARK Investment Management's Cathie Wood made a related point to investors in Hong Kong. Demand for HBM remains strong and supply is tight, she said, but "the trend is up, but the cycles are vicious. If you get a few more incremental competitors, especially out of China, the volatility will increase."

Others say the market has overreacted. Phillip Wool, chief market strategist at Rayliant Global Advisors, said the reaction looked disproportionate to the immediate threat. CXMT has not demonstrated large-scale production and still lags Samsung and SK Hynix in market share. "We're not even talking about HBM here, and the Korean chipmakers are still unquestionably dominating that space," Wool said. He read the selloff as "a sign of how vulnerable AI sentiment is at this moment."

Vey-Sern Ling, senior equity advisor at UBP, made a similar point. Chinese memory makers can potentially become a threat to the global demand-supply balance over time, he said, but in the short run they "continue to face technology hurdles," especially in advanced memory like HBM. Investors, he said, are "looking for excuses to take profit" on AI-related stocks that have outperformed this year.

The fundamentals still look strong

The companies being sold are posting large numbers. Micron reported fiscal fourth-quarter 2026 revenue of $54.23 billion, up 379.3% from a year earlier, with a non-GAAP gross margin of 87%. It guided fiscal first-quarter 2027 revenue to $61.5 billion.

On the Sept. 30 earnings call, CEO Sanjay Mehrotra said: "In calendar year 27 as well as 2028, we see demand exceeding supply." More than 75% of Micron's 2027 output is already committed, and the company has signed 26 Strategic Customer Agreements with take-or-pay volumes. The call made no direct reference to CXMT.

SK Hynix's preliminary second-quarter revenue was 79.32 trillion won, up 256.8% year over year, with operating profit of 60.54 trillion won.

One additional cost pressure: SK Hynix shares fell 2.3% earlier on reports that ASML will raise EUV and DUV replacement-part prices from 2027 for systems supplied to South Korea. A later report said SK Hynix has already accepted a 10% hike on ASML spare parts covering consumables and key components.

Who else is warning

Broadcom CEO Hock Tan told a conference in Singapore that "a lot of investors have no clue what they are investing in," and that they "set very extreme expectations, only to find out that it's almost like they are in a casino." Intel CEO Lip-Bu Tan, at the same event, said the rapid AI buildout could worsen hardware shortages, with memory stocks likely among the first to lose steam. The chief executives of Intel and Broadcom also warned that access to capital could emerge as a major headwind to the AI boom.

Wood pushed back on Hock Tan's speculative-excess concern, arguing AI still has the potential to drive substantial productivity gains.

What comes next

The immediate test was whether Samsung and SK Hynix could hold up once Seoul's regular session opened after those 6% premarket drops. They did not: the two fell more than 9% each on Thursday, and South Korea's Kospi lost 7.8%. Third-quarter earnings season will then show whether AI spending is slowing or merely being repriced. CoreWeave's 15% drop on debt concerns suggests the financing question is now getting as much attention as the CXMT news.