SD standards
"SD memory card" and "SD host device" are the umbrella descriptions for any memory card or device built to SD standards.[8] The SDA does not manufacture, market or sell any product. It exists solely to create industry standards and promote the adoption, advancement and use of SD standards. These standards are adopted by product manufacturers that make mechanical definitions and environmental requirements); File System Spec (definitions of the file system requirements in SD cards); SDIO and Intelligent SDIO card specifications (wireless LAN and TransferJet interface SD memory cards);[9] SD Host Controller Interface Spec; Advance Security SD specification, implementation and test guidelines.[10]
The SD Association was founded January 28, 2000 by SanDisk, Panasonic (Matsushita) and Toshiba – named also as "SD Group". The founding individual members include:
The SD Association held its first meeting on January 28, 2000, in San Francisco[1] and elected the first SDA Board of Directors on April 13.[11] The Board of Directors included 14 industry leaders from Alpine Electronics, Compaq, Eastman Kodak Company, Hewlett Packard, LG Electronics, Matsushita Electric, Mitsubishi Electronics, Motorola, NEC, Samsung, SanDisk Corporation, Sharp, Thomson and Toshiba Corporation. Shortly thereafter, SD v1.01 was released. The first SDIO specification was released in October 2001 and the miniSD released two years later in February 2003.[12] Multiple SD specifications were announced in 2004 including the First Advanced Security SD (ASSD), First Controller Interface and SD v1.10 with high-speed mode (25 MB/s).
MicroSD specifications [13] were released in 2005 with SD v2.0 SD- High Capacity (SDHC), introducing memory cards with up to 32 GB of storage in 2006.[14] SD v3.0 brought Extended Capacity (SDXC) [15] specifications offering memory cards with up to 2 TB of storage and Ultra High Speed – bus transfer speeds of up to 104 megabytes per second (MB/s) in 2009.[16] SD versions 4.0, v4.10 and v4.2 were introduced between 2011 and 2013. Version 4.0 included UHS-II interface specifications with bus transfer speeds of up to 312 MB/s and a new pin interface providing backwards compatibility.[16] Function Extension specifications and UHS Speed Class U1 were included in v4.10 while v4.2 contained UHS Speed Class U3 specification, supporting 4K video.[17] smartSD with NFC capabilities was introduced in 2013. September 2013 saw the first intelligent SDIO (iSDIO) specification along with a wireless LAN addendum.[9]
In February 2016, the SD Association introduced the Video Speed Class, which supports multi-file recording and video resolutions.[18] The Video Speed Class specifies minimum performance levels for 4K, 8K, 3D, and 360-degree video recording format.[19]
In November 2016, SD Specification 5.1 established the new Application Performance Class to meet technical and market requirements to both run and store applications on SD memory cards while still providing storage of pictures, videos, music, documents, and other data.[20] SD 5.1 introduced the first and most basic App Performance level, App Performance Class 1, or A1.[21] In February 2017, the SD Association expanded its App Performance Class with Application Performance Class 2 (A2), more than doubling random read and write speeds guaranteed in the entry-level App Performance Class 1. .[22]
In February 2017, the SD Association introduced UHS-III, doubling the fastest SD memory card transfer rate up to 624 MB/s.[23] UHS-III faster speeds help move large amounts of data generated by data-intense Gbit/s wireless communication, 360-degree cameras, drones, 3D, 4K and 8K videos recorded on SDXC and SDHC memory cards.[24]
In June 2018, the SD Association introduced SD Express[25][26] which added the PCI Express and NVMe interfaces to the legacy SD interface. The PCIe interface will deliver a 985 MB/s maximum data transfer rate and the NVMe upper layer protocol enables advanced memory access mechanisms.[27]
In tandem with the SD Express release, the SD Association also announced the SD Ultra Capacity (SDUC) card.[28] The maximum storage capacity in SD memory cards grows from 2 TB with SDXC to 128 TB with the SDUC card. Both releases maintained backward compatibility and are part of the new SD 7.0 specification.[29]
In February 2019, the SD Association announced the microSD Express.[30] The microSD Express cards offer PCI Express and NVMe interfaces, as the June 2018 SD Express release did, alongside the legacy microSD interface for continued backwards compatibility. The SDA also released new visual marks to denote microSD Express memory cards to make matching the card and device easier for optimal device performance.[31]
In May 2020, the SD Association introduced the SD 8.0 (SD8.0) specification for the SD Express memory card.
In May 2022, the SD Association announced the SD 9 Specification.
In October 2023, the SD Association announced the SD 9.1 Specification, which defines the access rules required to ensure the minimum defined performance of the PCI/NVMe interface in SD Express cards, including multi-stream access of up to eight streams.[32]
