Micron, Sandisk, Seagate, and Western Digital have become four of the hottest AI investment plays this year, all ranking among the S&P 500's top 10 performers. Sandisk leads with a roughly 575% year-to-date gain, followed by Micron at 240%, Seagate at about 210%, and Western Digital at over 170%. Since early 2025, Micron has surged about 920%, Western Digital 820%, and Seagate nearly 740%, versus a 25% S&P 500 gain. Sandisk, which spun off in February 2025, has jumped over 4,300%. The rally was driven by hyperscaler spending on AI data centers, which pushed memory demand beyond supply, giving producers strong pricing power. That momentum reversed in recent weeks, leaving the four stocks 20% to 40% below late-June peaks.
The companies occupy different niches in the memory and storage ecosystem, defined by a speed-versus-cost tradeoff across three technologies. DRAM, Micron's core product, is the fastest and most expensive. NAND, Sandisk's sole focus (also part of Micron's business), is slower but cheaper. Hard disk drives from Seagate and Western Digital are slowest but cheapest for bulk storage. These aren't substitutes, according to D.A. Davidson analyst Gil Luria: "They do different things." Micron CEO Sanjay Mehrotra echoed that, saying AI drives demand across the entire memory hierarchy, from high-bandwidth memory to DRAM to SSDs. He spoke from the site of Micron's planned $10 billion research facility in Boise, Idaho.
DRAM acts as a computer's short-term working memory, and it's stacked to make high-bandwidth memory (HBM), which moves data rapidly between GPUs and CPUs. Luria said HBM is "more important to the data center than CPUs are." Mehrotra, a 40-year chip industry veteran and Sandisk co-founder, said AI has fundamentally changed the memory business: "Today there is no AI without memory." Luria added that memory is now "the guts of the model," not a commodity accessory. Historically, DRAM producers competed on price, causing boom-and-bust cycles. Now HBM must be co-designed with processors, deepening supplier-customer relationships. Mehrotra said Micron can't produce enough, with data-center customers wanting about 50% more supply than the company can commit. Micron announced 16 long-term strategic customer agreements in June and has signed more since.
NAND retains data when power is off, making it useful for storing training datasets. Sandisk and Japan's Kioxia jointly manufacture NAND. Seagate and Western Digital primarily make HDDs, which use spinning magnetic disks rather than semiconductors, offering cheap storage for data not needing instant access. Western Digital only recently became a pure HDD player after separating from Sandisk in 2025. Luria noted that a data center buys a mix of HBM, DRAM, NAND, and disk drives depending on its needs. Mehrotra sees future demand from autonomous vehicles, robots, and AI-enabled devices. Luria sees Micron as particularly well positioned due to HBM's growing importance, calling its competitive advantage "Huge." The Club bought Micron on Aug. 11, believing its HBM exposure and customer agreements could sustain earnings and justify a higher valuation, despite the stock trading at a discount to semiconductor peers. (Jim Cramer's Charitable Trust is long MU.)
Source: CNBC