The Philadelphia Semiconductor Index (SOX) hit an all-time high of 14,655 on June 22, 2026, after rising more than 100% since the start of the year. Over the following five weeks, the index fell as much as 29% by late July, erasing more than $1 trillion in market capitalisation from leading chip stocks.
Several forces drove the sell-off, including weaker-than-expected AI chip guidance from Broadcom (NASDAQ: AVGO), rising bond yields, new U.S. tariff threats on chip exports, and growing concerns that valuations had outpaced earnings growth.
The index remained concentrated around its largest companies.
Just five names account for 38.23% of the SOX. Separately, Nvidia, Broadcom, Micron, Intel and Marvell are still the names that move the tape. Their combined influence shows how an index launched in 1993 to track a niche corner of the Philadelphia Stock Exchange became a key barometer of the global technology economy, a shift Disruption Banking examined last year through Light Street Capital’s “AI5” framework.
How Does a $200 Base Index From 1993 End Up Tracking the Entire AI Economy?
The SOX was launched by the Philadelphia Stock Exchange (PHLX) on December 1, 1993, at a base value of 200. Options trading began in September 1994, followed by a two-for-one index split in July 1995. Nasdaq acquired the PHLX in 2008 and incorporated the SOX into its global index business. The benchmark is now formally known as the PHLX Semiconductor Sector Index.
The SOX uses a modified market-capitalisation weighting system. Under the methodology adopted in April 2024, the three largest constituents by market capitalisation are capped at 12%, 10%, and 8% respectively at each quarterly rebalance. All other members are capped at 4%. Weights drift between rebalances as prices move, so several mid-tier names can sit above their 4% ceiling until the next rebalance restores the caps.
According to Nasdaq’s weighting file dated 30 June 2026, the five largest SOX constituents are Nvidia (NASDAQ: NVDA) at 10.34%, Micron Technology (NASDAQ: MU) at 8.65%, Broadcom at 7.69%, Applied Materials (NASDAQ: AMAT) at 5.84%, and KLA (NASDAQ: KLAC) at 5.71%. Those five names account for 38.23% of the index.
Applied Materials and KLA are the equipment names that rose with the HBM and foundry-tool boom; they now sit in the official top five even though they are not the stocks that usually set the daily tone.
The AI-infrastructure names that still set the tone for the tape sit across that list rather than neatly on top of it. Marvell is 5.29% and Intel is 4.43%. Taiwan Semiconductor Manufacturing Company (NYSE: TSM) carries a 4.15% weight because the SOX measures its ADR shares rather than its full global market capitalisation. ASML Holding (NASDAQ: ASML) sits at 4.49%. These weights update at each quarterly rebalance; the next reconstitution takes effect after the third Friday of September 2026.
Three Regime Changes That Rewired the SOX
The index’s nearly 33-year history reflects three major shifts in the semiconductor industry.
The Wintel Era (1993–2006)
The first era was dominated by Intel and the “Wintel” PC ecosystem. Intel designed and manufactured its processors in vertically integrated facilities and became the SOX’s dominant constituent. Texas Instruments (NASDAQ: TXN) was another major force. Manufacturing remained concentrated among Western companies using the integrated device manufacturer, or IDM, model, which combined chip design and fabrication.
The Rise of Fabless
The dot-com crash of 2000 reshaped the industry as chipmakers increasingly separated design from capital-intensive manufacturing. Taiwan Semiconductor Manufacturing Company expanded its foundry operations in Taiwan, allowing chip designers to outsource production.
When Apple (NASDAQ: AAPL) launched the iPhone in 2007, growing demand for outsourced mobile chips helped companies such as Qualcomm (NASDAQ: QCOM) and TSMC become global semiconductor leaders. The SOX’s centre of gravity shifted toward companies specialising in chip design and contract manufacturing.
The AI Supercycle
In 2012, researchers using Nvidia graphics processing units demonstrated their effectiveness in training neural networks, helping accelerate the modern deep-learning era.
The launch of ChatGPT in late 2022 sparked a surge in AI infrastructure spending as cloud companies committed hundreds of billions of dollars to data centres. Nvidia’s market capitalisation surpassed $5 trillion by October 2025 and later reached a record $5.5 trillion in May 2026, making it the world’s most valuable public company at the time.
The AI Names Still Driving the Tape in 2026
Each of the SOX’s current heavyweights occupies a distinct position in the AI infrastructure buildout.
Nvidia
Nvidia dominates AI data-centre compute. Its market capitalisation returned to approximately $5.5 trillion in late August 2026 after the company added more than $400 billion in market value following its fiscal Q2 2027 earnings on August 26.
Revenue more than doubled year over year, and management guided for roughly $108 billion in fiscal Q3 revenue. Separately, CEO Jensen Huang forecast about 70% annual revenue growth for fiscal 2028. Huang has cited $1 trillion of high-confidence demand through 2027. Nvidia shares have gained roughly 17% year to date, expanding investor interest into the memory and networking layers of the AI stack.
Micron Technology
Micron has become one of the biggest beneficiaries of the AI memory boom. It is a leading supplier of high-bandwidth memory, or HBM, for AI accelerators and ranks amongst the largest companies in the SOX by index weight.
Its fiscal third-quarter 2026 revenue climbed to $41.46 billion from $9.30 billion a year earlier. Micron reports its business in four segments; combined revenue from the Cloud Memory business unit ($13.77 billion) and the Core Data Center business unit ($11.52 billion) topped $25 billion in the quarter, with the remainder from Mobile and Client ($11.52 billion) and Automotive and Embedded ($4.63 billion).
Demand for HBM is also stretching well beyond the current quarter. CEO Sanjay Mehrotra said Micron has already sold out its entire 2026 HBM supply through binding multi-year agreements with customers. The company also started volume shipments of its HBM4 12-high stacks in early 2026 for Nvidia’s Vera Rubin platform.
Micron expects the HBM market to grow from roughly $35 billion in 2025 to about $100 billion by 2028. Its market capitalisation crossed $1 trillion in late May 2026.
Broadcom
Broadcom has become a key partner for hyperscalers developing custom AI silicon. CEO Hock Tan guided for $56 billion in AI semiconductor revenue for fiscal 2026, up roughly 180% from the prior year. Google, Meta Platforms (NASDAQ: META), and OpenAI are among its custom-chip co-design customers. Anthropic is also a named Broadcom customer, with more than 1 GW of TPU-based compute in 2026 and a further 5 GW beginning in 2027.
Multi-year co-design contracts underpin the customer pipeline, with deployment timelines extending through the end of the decade. Broadcom also supplies Tomahawk and Jericho switch chips that connect data-centre infrastructure, adding networking exposure as accelerator deployments grow.
Intel
Intel (NASDAQ: INTC) now accounts for 4.43% of the SOX, well below the dominance it held when the index launched in 1993. Its foundry division posted a $2.1 billion operating loss in the second quarter of 2026, down from $3.2 billion a year earlier, with an operating margin of −36%.
CEO Lip-Bu Tan has tied Intel’s turnaround to its 18A process node and plans to begin 14A high-volume manufacturing by 2028. Intel has yet to secure a major external foundry customer at scale for 18A. Meanwhile, Advanced Micro Devices (NASDAQ: AMD) holds approximately 34.5% of x86 server CPU unit share, according to Q2 2026 Mercury Research data.
Intel shares have rallied in 2026 on turnaround expectations, with foundry profitability remaining central to the company’s recovery.
Marvell Technology
Marvell is the least-recognised name among the SOX AI heavyweights, but its position has been earned by rising demand for custom AI silicon. In fiscal Q2 2027, reported on 27 August 2026, data-centre revenue reached a record $2.17 billion, up 46% year over year and 18% sequentially, and accounted for 79% of total sales. Management raised its fiscal 2027 revenue outlook to about $12 billion, implying roughly 45% growth, and now expects data-centre revenue to grow about 60% this fiscal year. For fiscal 2028 it guided to about $18 billion.
Marvell designs custom ASICs for Amazon’s Trainium accelerators, Microsoft’s Maia chips, and multi-year Google engagements, including an expanded commercial agreement covering TPU-ecosystem attach products. That co-design position places it in direct competition with Broadcom for the growing hyperscaler custom-silicon segment. Custom silicon accounted for roughly 18% of fiscal 2026 revenue. Management expects the custom business to ramp in the second half of fiscal 2027 and to more than double year over year in fiscal 2028.
Can the AI Infrastructure Hierarchy Survive Its Own Valuations?
The SOX’s 2026 performance highlights a valuation challenge for the semiconductor sector. Global chip sales remain strong, TSMC fabs are sold out into 2028, Broadcom’s custom-chip backlog exceeds $30 billion, and Marvell continues to post rapid data-centre growth.
The index’s 29% correction from its June peak reflected a repricing of those expectations after the SOX doubled in six months. Goldman Sachs prime brokerage data, reported by Reuters on 6 July, showed hedge funds net-selling semiconductor stocks for four consecutive weeks into early July, even as net exposure remained at the 98th percentile of the prior five years.
The key question is whether Nvidia, Broadcom, Micron, Intel, and Marvell can grow earnings fast enough to support peak valuations. That will partly depend on whether hyperscaler AI spending translates into measurable revenue and returns.
What Could Reshape the SOX Next?
With the official top five still close to 38% of the SOX, and Nvidia, Broadcom, Micron, Intel and Marvell still the names that move the tape, earnings surprises from that group can swing the whole benchmark. The next quarterly rebalance in September could also alter that concentration as market values and constituent weights reset.
Two developments stand out heading into year-end. Intel’s turnaround depends heavily on whether its 18A process can attract a major external foundry customer, while Marvell must convert growing demand for custom AI silicon into sustained revenue growth. Progress from either company could reshape the SOX’s top tier and further change the balance of power within the semiconductor industry.
Author: Demilola Esebame
See Also:
The AI5: The New Powerhouse Redefining the AI Era | Disruption Banking
Are Hedge Funds Abandoning the AI Trade After Four Weeks of Selling? | Disruption Banking
