The SD Card’s Next Chapter Begins with SD Express

The SD card is in its 25^th year as a staple for mobile devices. Throughout its history, it has powered the expansive growth of new devices and technologies with unprecedented levels of scale in capacity and performance.

Read our earlier article on the SD card’s first 25 years and how it was created.

In 2015, the SD card held a dominant position in the mobile storage market, but its future was far from certain.

For years, SD cards evolved through incremental improvements in flash memory density and controller efficiencies, steadily expanding their capabilities. Traditional standards were a success story, establishing the SD format’s dominance. However, UHS-I and UHS-II were also approaching a performance wall, topping out at 100 MB/s and 300 MB/s, respectively.

Since the early days of the SD card, the storage market has evolved rapidly. Phones, laptops, and other devices using embedded memory have been experiencing exponential performance growth, signaling that the next chapter of removable storage would require a fundamentally different approach.

"It became very clear and evident that we needed something faster and something that is scalable in terms of performance," recalled Jeff Tsujimoto, Sandisk director of product management, consumer products, and former SD Association board member.

In 2005, a 2GB SD card was revolutionary. A decade later, a single high-res video or a few photos could consume that capacity with ease. In addition, the use of cards evolved as they became more capable. Memory was no longer just a passive technology component; it had assumed a new role as a performance-critical enabler.

Seeing this uncertain future on the horizon, a cohort of engineers at Sandisk began to examine the technology and challenge themselves to design a new standard that would drive SD cards to new levels of performance and capacity.

When announced in 2018, the SD Express standard was characterized as a “quantum leap” not only in capacity but also in performance. The road getting there, however, was not quite a straightforward path. The breakthrough would come from abandoning incremental improvements entirely and embracing a fundamentally different approach to SD card architecture.

The big bet: embracing PCIe and NVMe

Around 2015, the SD Association encouraged member companies to develop a new version of SD cards that would future-proof them. Leaders at Sandisk, too, recognized the need to develop a new card that would meet evolving market needs. Cards needed to keep pace with other I/O and memory interfaces. After a thorough technical analysis and strategic study led by the CTO office at Sandisk, the company evaluated various options and saw an opportunity with PCIe and NVMe protocols, which were already known for performance breakthroughs in client-side SSDs.

The decision represented a strategic bet on PCIe and NVMe as the future of high-speed storage interfaces, leading Sandisk to write and submit a standardization proposal for their incorporation into SD cards to the SD Association in January 2017.

Yosi Pinto, a Senior Technologist in Consumer Products at Sandisk and the Chairman of the Board and President of the SD Association, explained: "We initiated the SD Express spec within the SD Association back in 2017, and Sandisk drove its proposal all the way, along with other leading companies that participate in the standardization process and contributed to their valuable inputs to the standard."

Driving the proposal forward, however, was only the beginning.

A primary concern was the requirements for thermal management. The PCIe interface and NVMe protocol enable significantly higher performance levels. Generally, better performance and higher data throughput inherently mean more electrical activity and switching, which generates heat.

Muralitharan Jayaraman, Director of Systems Design Engineering at Sandisk, said the need for an upgrade to SD cards was clear, and that it wouldn’t suffice to just “live with whatever we have today”. Despite hesitation from other companies in the industry, Jayaraman and his team at Sandisk wanted to move forward with confidence on the PCIe and NVMe implementation.

“With any new technology, you might not be comfortable”, he said. “But it’s important to have confidence, and that confidence is what helped us move forward.”

Jayaraman and various teams at the company led early efforts in testing and development on these initial challenges. As many as 1,000 engineers at different stages would work component by component to solve the complications around limited physical space and thermal management.

Removing roadblocks

The path from concept to working product required solving both technical and perception challenges.

Adapting PCIe and NVMe protocols to the SD form factor meant leveraging their built-in power management features—multiple power states, host-controlled transitions, and runtime idle modes—to manage thermal concerns.

But not all roadblocks were technical. There was also an existing mindset that PCIe had uses that were too power hungry for use in a postage-stamp-sized memory card.

“A challenge we were facing in the minds of a lot of people in the industry, including those at Sandisk, was that PCIe was mainly for data centers, and it was potentially coming to compute,” Tsujimoto said. “And those applications are very power hungry, much more than a little thumbnail-sized card can manage. So that was one of the challenges we had to overcome internally, as well as convincing partner companies within the SD Association to go along with this new specification.”

At the end of the day, Tsujimoto said, it came down to evaluating what was best for the company from a development perspective. While there were at least three viable platforms in consideration, it was clear that PCIe and NVME would provide the desired leap in capacity and performance capability.

Adoption accelerates

Since becoming available to consumers in 2023, Express cards have been in short supply at times. The challenge wasn’t a lack of demand—quite the opposite. “We did not predict the market to grow this big so quickly”, Jayaraman explained. “All of a sudden, it started expanding threefold what we estimated. We have had huge demand beyond our factory capacity”.

But that’s starting to shift. Gaming has become the first key market driving adoption. The adoption of SD Express by major handheld console companies marks a significant milestone for the standard.

“Gaming is usually at the forefront, because they need the faster performance", explained Sharlene Chin, Director of Product Management at Sandisk. “Other segments will take longer.”

Beyond gaming, other industries are beginning to recognize the potential in SD Express. Applications requiring real-time processing—from AI-powered surveillance systems that analyze video streams locally to compressed AI models that can run on smartphones and cars —are finding new possibilities in high-speed removable storage.

“We are now going through a turning point", Pinto observed. “From here, we will see more significant adoptions coming." SD Express represents more than just faster storage and larger capacities. It’s the foundation for entirely new applications that weren’t possible with traditional SD cards. “It can support high-speed data access required for AI-at-the-edge applications, rapid graphic files upload for gaming, run applications directly from the card, and more.”

A revolution ahead

What started as an urgent response to performance stagnation has grown into something much more ambitious. SD Express represents a fundamental change in how removable storage can function, from passive data repository to an active driver of new capabilities and possibly, like its SD predecessor, whole new classes of technology and devices.

“Up until SD Express, it’s been an incremental improvement", Chin reflected. “With SD Express, it’s a huge leap. You’re going up 10x what we could do before. It’s a whole new platform that we’re working on. So, it goes from slow evolution to a real revolution, a whole change.”

The implications extend beyond traditional use cases. Where once device manufacturers designed around storage limitations, SD Express invites them to reimagine what’s possible.

“I don’t think people have fully thought through what this card and the performance can unlock for their customers yet,” Chin observed.

The manufacturing foundation continues to evolve rapidly and will address supply limitations. Sandisk’s adoption of BiCS8 represents the kind of manufacturing evolution that will allow SD Express to scale, delivering cost reductions through higher die density alongside improved performance and power efficiency. The PCIe roadmap, meanwhile, extends through multiple generations, with Generation 7.0 released in 2025 and development already underway on Generation 8.

“PCIe gives us the future”, Chin said. “It gives us a pathway forward.”

For Sandisk, betting on PCIe and NVMe when the path seemed uncertain also meant convincing the industry to embrace a future where removable storage keeps pace with the exponential growth in computing performance.

The current wave of adoption represents just the foundation of what SD Express can enable. As manufacturing scales and costs decrease, the technology promises to unlock applications that today exist only in concept. What seemed like an uncertain future for removable storage in 2015 has become a glimpse into computing's next chapter, with most of the story still unwritten.