MicroSD Express: Doubling Speeds with SD 9.1 Revolution

The SD Association (SDA) has announced the introduction of the new microSD Express specification, poised to double its speed. Furthermore, four additional SD Express speed tiers have been incorporated to ensure a baseline sequential performance in the new SD 9.1 specification. This also encompasses support for multi-stream storage, accompanied by pertinent power and thermal management measures, to guarantee optimal performance.

The latest iteration of the microSD Express memory cards employs the NVMe upper-layer protocol for its PCIe interface. Leveraging the recently revised PCIe 4.0 x1 channel defined in the 8th edition of the microSD appendix, the interface speed can soar to an impressive 1969 MB/s, nearing 2 GB/s. This surge in speed grants product designers an expanded repertoire of storage solutions, empowering devices constrained by size, or those necessitating easy maintenance or upgradable storage, to attain SSD-caliber performance.

The SD Express speed tiers are dedicated to SDXC, SDUC, microSDXC, and microSDUC memory cards operating on the SD Express bus. With the relentless advancement of NAND flash technology, the evolution of storage technology has underscored the need for defining speeds, marking the most significant development since the inception of SD in 2000.

The SD 9.1 specification serves as a compass for consumers, aiding in the selection of memory cards tailored to their devices. It simultaneously furnishes manufacturers with novel tools to ascertain the minimum defined performance of the PCI/NVMe interface within SD Express memory cards. It also offers a panoply of methodologies to guide consumers in discerning the type of memory card that can ensure the seamless operation of specific applications. An official white paper has also been curated, shedding light on the novel features delineated in SD 9.1 and providing a deeper insight into the SD Express speed tiers.