One of the most significant quarterly data releases flew largely under the radar on August 14. That Friday marked the deadline for 13F filings, offering investors a window into the stock trading activity of Wall Street's top money managers, including Appaloosa Management's billionaire founder David Tepper, during the previous quarter.
Known for his long-term investment horizon and value-oriented approach, Tepper's Appaloosa portfolio frequently carries substantial weight in high-conviction themes like artificial intelligence. The second-quarter 13F filing revealed two notable moves: a major reduction in semiconductor giant Micron Technology (NASDAQ: MU) and a sixth consecutive quarter of accumulation in global foundry leader Taiwan Semiconductor Manufacturing (NYSE: TSM).
Tepper Slashes Second-Largest Position by 41%
During the period ending in June, Tepper exited more than a dozen positions, including SanDisk, but the market's focus centered on the sale of 690,000 shares of Micron. Despite the reduction, Micron remains Appaloosa's second-largest holding by market value, though the stake was trimmed by 41% this quarter.
The most likely catalyst for the sell-down is profit-taking. Micron's stock more than doubled in the second quarter, surpassing $1,200 per share. Context matters: Micron has been a core holding for Tepper's fund since mid-2023, and the shares have appreciated roughly 1,300% since then.
However, locking in gains may not tell the whole story. Over the past three decades, nearly every wave of emerging technology has experienced a bubble burst in its early innings. While Micron's high-bandwidth memory (HBM) demand remains red-hot with orders booked well in advance, historical patterns suggest that fully adapting and optimizing end-to-end AI solutions will still take years. Should an AI bubble deflate, Micron would likely be among the first to feel the impact.
The Billionaire Keeps Adding to Taiwan Semiconductor
On the other side of the ledger, David Tepper continues to aggressively build his stake in Taiwan Semiconductor Manufacturing. In the quarter ending June 30, he added another 322,500 shares, increasing that position by 24% and marking his sixth straight quarter of buying.
TSM's core value proposition lies in its role as the foundational infrastructure for AI computing power, a logic that also applies to Micron. As of September 30, 2025, Taiwan Semiconductor controlled nearly three-quarters of the global wafer foundry market. The company is aggressively expanding chip manufacturing capacity to boost GPU supply, and as long as graphics processing units remain in short supply, TSM will wield significant pricing power. With advanced-node chips accounting for a growing share of revenue, there is still upside for profit margins.
That said, Taiwan Semiconductor faces headwinds similar to Micron's. Despite its near-monopoly in foundry services, it remains exposed to the cyclical industry risks that have recurred throughout history. While long-term agreements with major customers provide cash flow visibility for several quarters ahead, shifting investor sentiment or interest rate hikes by the Federal Reserve could slow or even halt the near-vertical growth trajectory currently seen in the AI sector.