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Secure Digital
(SD, SDHC, SDXC, SDUC)

From top to bottom: SD, miniSD, microSD
Media type	Memory card
Capacity	SD: Up to 2 GB SDHC: over 2 GB to 32 GB SDXC: over 32 GB to 2 TB SDUC: over 2 TB to 128 TB
Block size	Variable
Read mechanism	Standard: 12.5 MB/s High-speed: 25 MB/s UHS-I: 50 MB/s or 104 MB/s UHS-II: 156 MB/s full-duplex, or 312 MB/s half-duplex UHS-III: 312 MB/s full-duplex, or 624 MB/s half-duplex Express: ≥ 985 MB/s full-duplex
Write mechanism	Variable
Standard	SD Standard
Developed by	SD Association
Dimensions	Standard: 32.0×24.0×2.1 mm (1.260×0.945×0.083 in) 1,612.8 mm (0.09842 cu in) Mini: 21.5×20.0×1.4 mm (0.846×0.787×0.055 in) 602 mm (0.0367 cu in) Micro: 15.0×11.0×1.0 mm (0.591×0.433×0.039 in) 165 mm (0.0101 cu in)
Weight	Standard: ~2 g Mini: ~800 mg Micro: ~250 mg
Usage	Portable devices, such as digital cameras and mobile phones (including most smartphones)
Extended from	MultiMediaCard
Released	August 1999

Secure Digital, officially abbreviated as SD, is a proprietary, non-volatile, flash memory card format the SD Association (SDA) developed for use in portable devices.

Because of their small physical dimensions, SD cards became widely used in many consumer electronic devices, such as digital cameras, camcorders, video game consoles, mobile phones, action cameras such as the GoPro Hero series, and camera drones.

The standard was introduced in August 1999 by SanDisk, Panasonic (Matsushita) and Toshiba as an improvement on MultiMediaCards (MMCs). SDs have become an industry standard. The three companies formed SD-3C, LLC, a company that licenses and enforces intellectual property (IP) rights associated with SD memory cards and SD host-and-ancillary products.

In January 2000, the companies formed the SD Association (SDA), a non-profit organization to create and promote SD Card standards. As of 2023, the SDA has approximately 1,000 member companies. It uses several SD-3C-owned trademarked logos to enforce compliance with its specifications and denote compatibility.

History

1999–2005: Creation and introduction of smaller formats

In 1999, SanDisk, Panasonic (Matsushita) and Toshiba agreed to develop and market the Secure Digital (SD) memory card. The card was derived from the MultiMediaCard (MMC) and provided digital rights management (DRM) based on the Secure Digital Music Initiative (SDMI) standard and a high memory density ("data/bits per physical space"), i.e. a large quantity of data could be stored in a small physical space.

SD was designed to compete with the Memory Stick, a flash storage format with DRM Sony had released the year before. Toshiba hoped the SD card’s DRM would encourage music suppliers concerned about piracy to use SD cards.

The trademarked SD logo was originally developed for the Super Density Disc, which was the unsuccessful Toshiba entry in the DVD format war. For this reason, the letter "D" is styled to resemble an optical disc.

At the 2000 Consumer Electronics Show (CES), the three companies announced the creation of the SD Association (SDA) to promote SD cards. The SD Association, which was headquartered in San Ramon, California, United States, then had 30 member companies and product manufacturers that made interoperable memory cards and devices. Early samples of the SD card became available in the first quarter of 2000, and production quantities of 32 and 64 megabyte (MB) cards became available three months later. The first 64 MB cards were offered for sale for 200 USD. SD was envisioned as a single memory card format for several kinds of electronic devices, that could also function as an expansion slot for adding new capabilities for a device. The first 256 MB and 512 MB SD cards were announced in 2001.

miniSD

At March 2003 CeBIT, SanDisk Corporation introduced, announced and demonstrated the miniSD form factor. The SDA adopted the miniSD card in 2003 as a small-form-factor extension to the SD card standard. While the new cards were designed for mobile phones, they were usually packaged with a miniSD adapter that provided compatibility with a standard SD memory card slot.

microSD

MicroSD form-factor memory cards were introduced in 2004 by SanDisk at CeBIT and originally called T-Flash, and later TransFlash, commonly abbreviated to "TF". T-Flash was renamed microSD in 2005 when it was adopted by the SDA. TransFlash and microSD cards are functionally identical, allowing either to operate in devices made for the other. A passive adapter allows the use of microSD and TransFlash cards in SD card slots.

2006–2008: SDHC and SDIO

In September 2006, SanDisk announced the 4 GB miniSDHC. Like the SD and SDHC, the miniSDHC card has the same form factor as the older miniSD card but the HC card requires HC support built into the host device. Devices that support miniSDHC work with miniSD and miniSDHC, but devices without specific support for miniSDHC work only with the older miniSD card. Since 2008, miniSD cards are no longer produced, due to market domination of the even smaller microSD cards.

2009–2019: SDXC

The storage density of memory cards increased significantly throughout the 2010s, allowing the earliest devices to offer support for the SD:XC standard, such as the Samsung Galaxy S III and Samsung Galaxy Note II mobile phones, to expand their available storage to several hundreds of gigabytes.

In January 2009, the SDA announced the SDXC family, which supports cards up to 2 TB and speeds up to 300 MB/s. SDXC cards are formatted with the exFAT file system by default. SDXC was announced at the Consumer Electronics Show (CES) 2009 (January 7–10). At the same show, SanDisk and Sony also announced a comparable Memory Stick XC variant with the same 2 TB maximum as SDXC, and Panasonic announced plans to produce 64 GB SDXC cards. On March 6, Pretec introduced the first SDXC card, a 32 GB card with a read/write speed of 400 Mbit/s. But only early in 2010 did compatible host devices come onto the market, including Sony's Handycam HDR-CX55V camcorder, Canon's EOS 550D (also known as Rebel T2i) Digital SLR camera, a USB card reader from Panasonic, and an integrated SDXC card reader from JMicron. The earliest laptops to integrate SDXC card readers relied on a USB 2.0 bus, which does not have the bandwidth to support SDXC at full speed.

In early 2010, commercial SDXC cards appeared from Toshiba (64 GB), Panasonic (64 GB and 48 GB), and SanDisk (64 GB).

In early 2011, Centon Electronics, Inc. (64 GB and 128 GB) and Lexar (128 GB) began shipping SDXC cards rated at Speed Class 10. Pretec offered cards from 8 GB to 128 GB rated at Speed Class 16. In September 2011, SanDisk released a 64 GB microSDXC card. Kingmax released a comparable product in 2011.

In April 2012, Panasonic introduced MicroP2 card format for professional video applications. The cards are essentially full-size SDHC or SDXC UHS-II cards, rated at UHS Speed Class U1. An adapter allows MicroP2 cards to work in current P2 card equipment.

Panasonic MicroP2 cards shipped in March 2013 and were the first UHS-II compliant products on market; initial offer includes a 32 GB SDHC card and a 64 GB SDXC card. Later that year, Lexar released the first 256 GB SDXC card, based on 20 nm NAND flash technology.

In February 2014, SanDisk introduced the first 128 GB microSDXC card, which was followed by a 200 GB microSDXC card in March 2015. September 2014 saw SanDisk announce the first 512 GB SDXC card.

Samsung announced the world's first EVO Plus 256 GB microSDXC card in May 2016, and in September 2016 Western Digital (SanDisk) announced that a prototype of the first 1 TB SDXC card would be demonstrated at Photokina.

In August 2017, SanDisk launched a 400 GB microSDXC card.

In January 2018, Integral Memory unveiled its 512 GB microSDXC card. In May 2018, PNY launched a 512 GB microSDXC card. In June 2018 Kingston announced its Canvas series of microSD cards which were capable of capacities up to 512 GB, in three variations, Select, Go! and React.

In February 2019, Micron and SanDisk unveiled their microSDXC cards of 1 TB capacity.

2019–present: SDUC

The Secure Digital Ultra Capacity (SDUC) format supports cards up to 128 TB and offers speeds up to 985 MB/s.

In April 2024, Western Digital (SanDisk) revealed the world's first 4 TB SD card at NAB 2024, which will make use of the SDUC format. It is set to release in 2025.

Capacity

Secure Digital includes five card families available in three form factors. The five families are the original standard capacity (SDSC), high capacity (SDHC), extended capacity (SDXC), ultra capacity (SDUC) and SDIO, which combines input/output functions with data storage.

Comparison of SD card capacity standards

		SD (SDSC)	SDHC	SDXC	SDUC
Logo
Year		1999	2006	2009	2018
Capacity	Min	—	>2 GB	>32 GB	>2 TB
	Max	2 GB	32 GB	2 TB	128 TB
Typical FS		FAT12/FAT16	FAT32	exFAT

SD (SDSC)

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The second-generation Secure Digital (SDSC or Secure Digital Standard Capacity) card was developed to improve on the MultiMediaCard (MMC) standard, which continued to evolve, but in a different direction. Secure Digital changed the MMC design in several ways:

• Asymmetrical shape of the sides of the SD card prevents inserting it upside down (whereas an MMC goes in most of the way but makes no contact if inverted).
• Most standard size SD cards are 2.1 mm (0.083 inches) thick, with microSD versions being 1.0 mm (0.039 inches) thick, compared to 1.4 mm (0.055 inches) for MMCs. The SD specification defines a card called Thin SD with a thickness of 1.4 mm, but they occur only rarely, as the SDA went on to define even smaller form factors.
• The card's electrical contacts are recessed beneath the surface of the card, protecting them from contact with a user's fingers.
• The SD specification envisioned capacities and transfer rates exceeding those of MMC, and both of these functionalities have grown over time. For a comparison table, see below.
• While MMC uses a single pin for data transfers, the SD card added a four-wire bus mode for higher data rates.
• The SD card added Content Protection for Recordable Media (CPRM) security circuitry for digital rights management (DRM) content-protection.
• Addition of a write-protect notch

Full-size SD cards do not fit into the slimmer MMC slots, and other issues also affect the ability to use one format in a host device designed for the other.

SDHC

The Secure Digital High Capacity (SDHC) format, announced in January 2006 and defined in version 2.0 of the SD specification, supports cards with capacities up to 32 GB. The SDHC trademark is licensed to ensure compatibility.

SDHC cards are physically and electrically identical to standard-capacity SD cards (SDSC). The major compatibility issues between SDHC and SDSC cards are the redefinition of the Card-Specific Data (CSD) register in version 2.0 (see below), and the fact that SDHC cards are shipped preformatted with the FAT32 file system.

Version 2.0 also introduces a high-speed bus mode for both SDSC and SDHC cards, which doubles the original Standard Speed clock to produce 25 MB/s.

SDHC host devices are required to accept older SD cards. However, older host devices do not recognize SDHC or SDXC memory cards, although some devices can do so through a firmware upgrade. Older Windows operating systems released before Windows 7 require patches or service packs to support access to SDHC cards.

SDXC

The Secure Digital eXtended Capacity (SDXC) format, announced in January 2009 and defined in version 3.01 of the SD specification, supports cards up to 2 TB, compared to a limit of 32 GB for SDHC cards in the SD 2.0 specification. SDXC adopts Microsoft's exFAT file system as a mandatory feature.

Version 3.01 also introduced the Ultra High Speed (UHS) bus for both SDHC and SDXC cards, with interface speeds from 50 MB/s to 104 MB/s for four-bit UHS-I bus. (this number has since been exceeded with SanDisk proprietary technology for 170 MB/s read, which is not proprietary anymore, as Lexar has the 1066x running at 160 MB/s read and 120 MB/s write via UHS 1, and Kingston also has their Canvas Go! Plus, also running at 170 MB/s).

Version 4.0, introduced in June 2011, allows speeds of 156 MB/s to 312 MB/s over the four-lane (two differential lanes) UHS-II bus, which requires an additional row of physical pins.

Version 5.0 was announced in February 2016 at CP+ 2016, and added "Video Speed Class" ratings for UHS cards to handle higher resolution video formats like 8K. The new ratings define a minimal write speed of 90 MB/s.

SDUC

The Secure Digital Ultra Capacity (SDUC) format, described in the SD 7.0 specification, and announced in June 2018, supports cards up to 128 TB and offers speeds up to 985 MB/s, regardless of form factor, either micro or full size, or interface type including UHS-I, UHS-II, UHS-III or SD Express. The SD Express interface can also be used with SDHC and SDXC cards.

exFAT filesystem

SDXC and SDUC cards are required to be formatted using exFAT, but many operating systems will support others.

Windows Vista (SP1) and later and OS X (10.6.5 and later) have native support for exFAT. (Windows XP and Server 2003 can support exFAT via an optional update from Microsoft.)

Most BSD and Linux distributions did not have exFAT support for legal reasons, though in Linux kernel 5.4 Microsoft open-sourced the spec and allowed the inclusion of an exFAT driver. Users of older kernels or BSD can manually install third-party implementations of exFAT (as a FUSE module) in order to be able to mount exFAT-formatted volumes. However, SDXC cards can be reformatted to use any file system (such as ext4, UFS, VFAT or NTFS), alleviating the restrictions associated with exFAT availability.

Except for the change of file system, SDXC cards are mostly backward compatible with SDHC readers, and many SDHC host devices can use SDXC cards if they are first reformatted to the FAT32 file system.

The SD Association provides a formatting utility for Windows and Mac OS X that checks and formats SD, SDHC, SDXC and SDUC cards.

Speed

SD card speed is customarily rated by its sequential read or write speed. The sequential performance aspect is the most relevant for storing and retrieving large files (relative to block sizes internal to the flash memory), such as images and multimedia. Small data (such as file names, sizes and timestamps) falls under the much lower speed limit of random access, which can be the limiting factor in some use cases.

With early SD cards, a few card manufacturers specified the speed as a "times" ("×") rating, which compared the average speed of reading data to that of the original CD-ROM drive. This was superseded by the Speed Class Rating, which guarantees a minimum rate at which data can be written to the card.

The newer families of SD card improve card speed by increasing the bus rate (the frequency of the clock signal that strobes information into and out of the card). Whatever the bus rate, the card can signal to the host that it is "busy" until a read or a write operation is complete. Compliance with a higher speed rating is a guarantee that the card limits its use of the "busy" indication.

Bus

Default Speed

SD cards will read and write at speeds of 12.5 MB/s.

High Speed

High-Speed Mode (25 MB/s) was introduced to support digital cameras with 1.10 spec version.

Ultra High Speed (UHS)

The Ultra High Speed (UHS) bus is available on some SDHC and SDXC cards.

Cards that comply with UHS show Roman numerals 'I', 'II' or 'III' next to the SD card logo, and report this capability to the host device. Use of UHS-I requires that the host device command the card to drop from 3.3-volt to 1.8-volt operation over the I/O interface pins and select the four-bit transfer mode, while UHS-II requires 0.4-volt operation.

The higher speed rates of UHS-II and III are achieved by using two-lane 0.4 V low-voltage differential signaling (LVDS) on a second row of pins. Each lane is capable of transferring up to 156 MB/s. In full-duplex mode, one lane is used for Transmit while the other is used for Receive. In half-duplex mode both lanes are used for the same direction of data transfer allowing a double data rate at the same clock speed. In addition to enabling higher data rates, the UHS-II interface allows for lower interface power consumption, lower I/O voltage and lower electromagnetic interference (EMI).

The following ultra-high speeds are specified:

UHS-I

Specified in SD version 3.01. Supports a clock frequency of 100 MHz (a quadrupling of the original "Default Speed"), which in four-bit transfer mode could transfer 50 MB/s (SDR50). UHS-I cards declared as UHS104 (SDR104) also support a clock frequency of 208 MHz, which could transfer 104 MB/s. Double data rate operation at 50 MHz (DDR50) is also specified in Version 3.01, and is mandatory for microSDHC and microSDXC cards labeled as UHS-I. In this mode, four bits are transferred when the clock signal rises and another four bits when it falls, transferring an entire byte on each full clock cycle, hence a 50 MB/s operation could be transferred using a 50 MHz clock.

There is a proprietary UHS-I extension, called DDR200, originally created by SanDisk that increases transfer speed further to 170 MB/s. Unlike UHS-II, it does not use additional pins. It achieves this by using the 208 MHz frequency of the standard SDR104 mode, but using DDR transfers. This extension has since then been used by Lexar for their 1066x series (160 MB/s), Kingston Canvas Go Plus (170 MB/s) and the MyMemory PRO SD card (180 MB/s).

UHS-II

Specified in version 4.0, further raises the data transfer rate to a theoretical maximum of 156 MB/s (full-duplex) or 312 MB/s (half-duplex) using an additional row of pins for LVDS signalling (a total of 17 pins for full-size and 16 pins for micro-size cards). While first implementations in compact system cameras were seen three years after specification (2014), it took many more years until UHS-II was implemented on a regular basis. At the beginning of 2024, almost 90 DSLR and mirrorless cameras support UHS-II.

UHS-III

Version 6.0, released in February 2017, added two new data rates to the standard. FD312 provides 312 MB/s while FD624 doubles that. Both are full-duplex. The physical interface and pin-layout are the same as with UHS-II, retaining backward compatibility.

SD Express

The SD Express bus was released in June 2018 with SD specification 7.0. It uses a single PCIe lane to provide full-duplex 985 MB/s transfer speed. Supporting cards must also implement the NVM Express storage access protocol. The Express bus can be implemented by SDHC, SDXC and SDUC cards. For legacy application use, SD Express cards must also support High-Speed bus and UHS-I bus. The Express bus re-uses the pin layout of UHS-II cards and reserves the space for additional two pins that may be introduced in the future.

Hosts which implement version 7.0 of the spec allow SD Cards to do direct memory access, which increases the attack surface of the host dramatically in the face of malicious SD cards.

Version 8.0 was announced on 19 May 2020, with support for two PCIe lanes with an additional row of contacts and PCIe 4.0 transfer rates, for a maximum bandwidth of 3,938 MB/s.

Version 9.0 was released in February 2022.

Version 9.1 was announced in October 2023.

microSD Express

In February 2019, the SD Association announced microSD Express. 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 visual marks to denote microSD Express memory cards to make matching the card and device easier for optimal device performance.

Bus speed comparison

Comparison of SD card bus speeds

Bus interface	Bus logo	Bus speed	PCI Express lanes	Duplex	Card types				Spec version
					SD	SDHC	SDXC	SDUC
Default Speed	—	00,012.5 MB/s	—	?	Yes	Yes	Yes	Yes	1.01
High Speed		0025 MB/s							1.10
UHS-I		0050 MB/s		Half / Full	No				3.01
		0104 MB/s		Half
	—	0180 MB/s							—
UHS-II		0156 MB/s		Full					4.00
		0312 MB/s		Half
UHS-III		0312 MB/s		Full					6.00
		0624 MB/s
SD Express		0985 MB/s	3.1 ×1						7.00
		1,969 MB/s	3.1 ×2						8.00
			4.0 ×1
		3,938 MB/s	4.0 ×2

Compatibility

NOTE: If the card reader uses the DDR208 controller on the UHS 1 pins, the card reader will perform at 180 MB/s on applicable UHS 1 cards

Class

The SD Association defines standard speed classes for SDHC/SDXC cards indicating minimum performance (minimum serial data writing speed). Both read and write speeds must exceed the specified value. The specification defines these classes in terms of performance curves that translate into the following minimum read-write performance levels on an empty card and suitability for different applications:

The SD Association defines three types of Speed Class ratings: the original Speed Class, UHS Speed Class and Video Speed Class.

(Original) Speed Class

Speed Class ratings 2, 4 and 6 assert that the card supports the respective number of megabytes per second as a minimum sustained write speed for a card in a fragmented state.

Class 10 asserts that the card supports 10 MB/s as a minimum non-fragmented sequential write speed and uses a High Speed bus mode. The host device can read a card's speed class and warn the user if the card reports a speed class that falls below an application's minimum need. By comparison, the older "×" rating measured maximum speed under ideal conditions, and was vague as to whether this was read speed or write speed.

The graphical symbol for the speed class has a number encircled with 'C' (C2, C4, C6 and C10).

UHS Speed Class

UHS-I and UHS-II cards can use UHS Speed Class rating with two possible grades: class 1 for minimum write performance of at least 10 MB/s ('U1' symbol featuring number 1 inside 'U') and class 3 for minimum write performance of 30 MB/s ('U3' symbol featuring 3 inside 'U'), targeted at recording 4K video. Before November 2013, the rating was branded UHS Speed Grade and contained grades 0 (no symbol) and 1 ('U1' symbol). Manufacturers can also display standard speed class symbols (C2, C4, C6 and C10) alongside, or in place of UHS speed class.

UHS memory cards work best with UHS host devices. The combination lets the user record HD resolution videos with tapeless camcorders while performing other functions. It is also suitable for real-time broadcasts and capturing large HD videos.

Video Speed Class

Video Speed Class defines a set of requirements for UHS cards to match the modern MLC NAND flash memory and supports progressive 4K and 8K video with minimum sequential writing speeds of 6 – 90 MB/s. The graphical symbols use a stylized 'V' followed by a number designating write speed (i.e. V6, V10, V30, V60 and V90).

SD Express Speed Class

Version 9.1 of the SD specification, introduced in October 2023, defines new SD Express speed classes. The graphical symbols use a stylized 'E' followed by a number designating the minimum read/write speed. The specified classes are E150, E300, E450 and E600.

Comparison

Comparison of SD card Speed Class ratings

Minimum sequential writing speed	Suggested max. bitrate	Speed Class			Video format
		Speed Class	UHS Speed Class	Video Speed Class	SD	HD / Full HD	4K	8K
02 MB/s	015 Mbit/s	Class 2 (C2)	—	—	Yes	No	No	No
04 MB/s	030 Mbit/s	Class 4 (C4)				Yes
06 MB/s	045 Mbit/s	Class 6 (C6)		Class 6 (V6)			Yes
10 MB/s	075 Mbit/s	Class 10 (C10)	Class 1 (U1)	Class 10 (V10)
30 MB/s	220 Mbit/s		Class 3 (U3)	Class 30 (V30)				Yes
60 MB/s	460 Mbit/s			Class 60 (V60)
90 MB/s	700 Mbit/s			Class 90 (V90)

Application Performance Class

Application Performance Class is a newly defined standard from the SD Specification 5.1 and 6.0 which not only define sequential Writing Speeds but also mandates a minimum IOPS for reading and writing. Class A1 requires a minimum of 1,500 reading and 500 writing operations per second using 4 kbytes blocks, while class A2 requires 4,000 and 2,000 IOPS. A2 class cards require host driver support as they use command queuing and write caching to achieve their higher speeds. Without they are guaranteed to at least reach A1 speeds. As of Linux kernel 5.15, it fully supports A2.

Comparison of SD card Application Performance Class ratings

Name	Minimum random IOPS		Minimum sustained sequential writing
	Read	Write
Application Performance Class 1 (A1)	1,500 IOPS	0500 IOPS	10 MB/s
Application Performance Class 2 (A2)	4,000 IOPS	2,000 IOPS

"×" rating

Rating	Approx. (MB/s)	Comparable speed class
16×	2.34	(13×)
32×	4.69	(27×)
48×	7.03	(40×)
100×	14.6	(67×)

The "×" rating, which was used by some card manufacturers and made obsolete by speed classes, is a multiple of the standard CD-ROM drive speed of 150 KB/s (approximately 1.23 Mbit/s). Basic cards transfer data at up to six times (6×) the CD-ROM speed; that is, 900 kbit/s or 7.37 Mbit/s. The 2.0 specification defines speeds up to 200×, but is not as specific as Speed Classes are on how to measure speed. Manufacturers may report best-case speeds and may report the card's fastest read speed, which is typically faster than the write speed. Some vendors, including Transcend and Kingston, report their cards' write speed. When a card lists both a speed class and an "×" rating, the latter may be assumed a read speed only.

Real-world performance

In applications that require sustained write throughput, such as video recording, the device might not perform satisfactorily if the SD card's class rating falls below a particular speed. For example, a high-definition camcorder may require a card of not less than Class 6, suffering dropouts or corrupted video if a slower card is used. Digital cameras with slow cards may take a noticeable time after taking a photograph before being ready for the next, while the camera writes the first picture.

The speed class rating does not totally characterize card performance. Different cards of the same class may vary considerably while meeting class specifications. A card's speed depends on many factors, including:

• The frequency of soft errors that the card's controller must re-try
• Write amplification: The flash controller may need to overwrite more data than requested. This has to do with performing read-modify-write operations on write blocks, freeing up (the much larger) erase blocks, while moving data around to achieve wear leveling.
• File fragmentation: where there is not sufficient space for a file to be recorded in a contiguous region, it is split into non-contiguous fragments. This does not cause rotational or head-movement delays as with electromechanical hard drives, but may decrease speed⁠—for instance, by requiring additional reads and computation to determine where on the card the file's next fragment is stored.

In addition, speed may vary markedly between writing a large amount of data to a single file (sequential access, as when a digital camera records large photographs or videos) and writing a large number of small files (a random-access use common in smartphones). A study in 2012 found that, in this random-access use, some Class 2 cards achieved a write speed of 1.38 MB/s, while all cards tested of Class 6 or greater (and some of lower Classes; lower Class does not necessarily mean better small-file performance), including those from major manufacturers, were over 100 times slower. In 2014, a blogger measured a 300-fold performance difference on small writes; this time, the best card in this category was a class 4 card.

Features

Card security

Commands to disable writes

The host device can command the SD card to become read-only (to reject subsequent commands to write information to it). There are both reversible and irreversible host commands that achieve this.

Write-protect notch

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Most full-size SD cards have a "mechanical write protect switch" allowing the user to advise the host computer that the user wants the device to be treated as read-only. This does not protect the data on the card if the host is compromised: "It is the responsibility of the host to protect the card. The position of the write protect switch is unknown to the internal circuitry of the card." Some host devices do not support write protection, which is an optional feature of the SD specification, and drivers and devices that do obey a read-only indication may give the user a way to override it.

The switch is a sliding tab that covers a notch in the card. The miniSD and microSD formats do not directly support a write protection notch, but they can be inserted into full-size adapters which do.

When looking at the SD card from the top, the right side (the side with the beveled corner) must be notched.

On the left side, there may be a write-protection notch. If the notch is omitted, the card can be read and written. If the card is notched, it is read-only. If the card has a notch and a sliding tab which covers the notch, the user can slide the tab upward (toward the contacts) to declare the card read/write, or downward to declare it read-only. The diagram to the right shows an orange sliding write-protect tab in both the unlocked and locked positions.

Cards sold with content that must not be altered are permanently marked read-only by having a notch and no sliding tab.

Card password

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A host device can lock an SD card using a password of up to 16 bytes, typically supplied by the user. A locked card interacts normally with the host device except that it rejects commands to read and write data. A locked card can be unlocked only by providing the same password. The host device can, after supplying the old password, specify a new password or disable locking. Without the password (typically, in the case that the user forgets the password), the host device can command the card to erase all the data on the card for future re-use (except card data under DRM), but there is no way to gain access to the existing data.

Windows Phone 7 devices use SD cards designed for access only by the phone manufacturer or mobile provider. An SD card inserted into the phone underneath the battery compartment becomes locked "to the phone with an automatically generated key" so that "the SD card cannot be read by another phone, device, or PC". Symbian devices, however, are some of the few that can perform the necessary low-level format operations on locked SD cards. It is therefore possible to use a device such as the Nokia N8 to reformat the card for subsequent use in other devices.

smartSD cards

A smartSD memory card is a microSD card with an internal "secure element" that allows the transfer of ISO 7816 Application Protocol Data Unit commands to, for example, JavaCard applets running on the internal secure element through the SD bus.

Some of the earliest versions of microSD memory cards with secure elements were developed in 2009 by DeviceFidelity, Inc., a pioneer in near-field communication (NFC) and mobile payments, with the introduction of In2Pay and CredenSE products, later commercialized and certified for mobile contactless transactions by Visa in 2010. DeviceFidelity also adapted the In2Pay microSD to work with the Apple iPhone using the iCaisse, and pioneered the first NFC transactions and mobile payments on an Apple device in 2010.

Various implementations of smartSD cards have been done for payment applications and secured authentication. In 2012 Good Technology partnered with DeviceFidelity to use microSD cards with secure elements for mobile identity and access control.

microSD cards with Secure Elements and NFC (near-field communication) support are used for mobile payments, and have been used in direct-to-consumer mobile wallets and mobile banking solutions, some of which were launched by major banks around the world, including Bank of America, US Bank and Wells Fargo, while others were part of innovative new direct-to-consumer neobank programs such as moneto, first launched in 2012.

microSD cards with Secure Elements have also been used for secure voice encryption on mobile devices, which allows for one of the highest levels of security in person-to-person voice communications. Such solutions are heavily used in intelligence and security.

In 2011, HID Global partnered with Arizona State University to launch campus access solutions for students using microSD with Secure Element and MiFare technology provided by DeviceFidelity, Inc. This was the first time regular mobile phones could be used to open doors without need for electronic access keys.

Vendor enhancements

Vendors have sought to differentiate their products in the market through various vendor-specific features:

• Integrated Wi-Fi – Several companies produce SD cards with built-in Wi-Fi transceivers supporting static security (WEP 40/104/128, WPA-PSK and WPA2-PSK). The card lets any digital camera with an SD slot transmit captured images over a wireless network, or store the images on the card's memory until it is in range of a wireless network. Examples include: Eye-Fi / SanDisk, Transcend Wi-Fi, Toshiba FlashAir, Trek Flucard, PQI Air Card and LZeal ez Share. Some models geotag their pictures.
• Pre-loaded content – In 2006, SanDisk announced Gruvi, a microSD card with extra digital rights management features, which they intended as a medium for publishing content. SanDisk again announced pre-loaded cards in 2008, under the slotMusic name, this time not using any of the DRM capabilities of the SD card. In 2011, SanDisk offered various collections of 1000 songs on a single slotMusic card for about $40, now restricted to compatible devices and without the ability to copy the files.
• Integrated USB connector – The SanDisk SD Plus product can be plugged directly into a USB port without needing a USB card reader. Other companies introduced comparable products, such as the Duo SD product of OCZ Technology and the 3 Way (microSDHC, SDHC and USB) product of A-DATA, which was available in 2008 only.
• Different colors – SanDisk has used various colors of plastic or adhesive label, including a "gaming" line in translucent plastic colors that indicated the card's capacity. In 2006, the first 256MB microSD to used color-coded cards by Kingmax, which later other brands (e.g., SanDisk, Kioxia) had been implemented to this day.
• Integrated display – In 2006, ADATA announced a Super Info SD card with a digital display that provided a two-character label and showed the amount of unused memory on the card.

SDIO cards

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A SDIO (Secure Digital Input Output) card is an extension of the SD specification to cover I/O functions. SDIO cards are only fully functional in host devices designed to support their input-output functions (typically PDAs like the Palm Treo, but occasionally laptops or mobile phones). These devices can use the SD slot to support GPS receivers, modems, barcode readers, FM radio tuners, TV tuners, RFID readers, digital cameras and interfaces to Wi-Fi, Bluetooth, Ethernet and IrDA. Many other SDIO devices have been proposed, but it is now more common for I/O devices to connect using the USB interface.

SDIO cards support most of the memory commands of SD cards. SDIO cards can be structured as eight logical cards, although currently, the typical way that an SDIO card uses this capability is to structure itself as one I/O card and one memory card.

The SDIO and SD interfaces are mechanically and electrically identical. Host devices built for SDIO cards generally accept SD memory cards without I/O functions. However, the reverse is not true, because host devices need suitable drivers and applications to support the card's I/O functions. For example, an HP SDIO camera usually does not work with PDAs that do not list it as an accessory. Inserting an SDIO card into any SD slot causes no physical damage nor disruption to the host device, but users may be frustrated that the SDIO card does not function fully when inserted into a seemingly compatible slot. (USB and Bluetooth devices exhibit comparable compatibility issues, although to a lesser extent thanks to standardized USB device classes and Bluetooth profiles.)

The SDIO family comprises Low-Speed and Full-Speed cards. Both types of SDIO cards support Serial Peripheral Interface (SPI) and one-bit SD bus types. Low-Speed SDIO cards are allowed to also support the four-bit SD bus; Full-Speed SDIO cards are required to support the four-bit SD bus. To use an SDIO card as a "combo card" (for both memory and I/O), the host device must first select four-bit SD bus operation. Two other unique features of Low-Speed SDIO are a maximum clock rate of 400 kHz for all communications, and the use of Pin 8 as "interrupt" to try to initiate dialogue with the host device.

Compatibility

Host devices that comply with newer versions of the specification provide backward compatibility and accept older SD cards. For example, SDXC host devices accept all previous families of SD memory cards, and SDHC host devices also accept standard SD cards.

Older host devices generally do not support newer card formats, and even when they might support the bus interface used by the card, there are several factors that arise:

• A newer card may offer greater capacity than the host device can handle (over 4 GB for SDHC, over 32 GB for SDXC).
• A newer card may use a file system the host device cannot navigate (FAT32 for SDHC, exFAT for SDXC)
• Use of an SDIO card requires the host device be designed for the input/output functions the card provides.
• The hardware interface of the card was changed starting with the version 2.0 (new high-speed bus clocks, redefinition of storage capacity bits) and SDHC family (ultra-high speed (UHS) bus)
• UHS-II has physically more pins but is backwards compatible to UHS-I and non-UHS for both slot and card.
• Some vendors produced SDSC cards above 1 GB before the SDA had standardized a method of doing so.

Markets

Due to their compact size, Secure Digital cards are used in many consumer electronic devices, and have become a widespread means of storing several gigabytes of data in a small size. Devices in which the user may remove and replace cards often, such as digital cameras, camcorders and video game consoles, tend to use full-sized cards. Devices in which small size is paramount, such as mobile phones, action cameras such as the GoPro Hero series, and camera drones, tend to use microSD cards.

Mobile phones

The microSD card has helped propel the smartphone market by giving both manufacturers and consumers greater flexibility and freedom.

While cloud storage depends on stable internet connection and sufficiently voluminous data plans, memory cards in mobile devices provide location-independent and private storage expansion with much higher transfer rates and no network delay, enabling applications such as photography and video recording. While data stored internally on bricked devices is inaccessible, data stored on the memory card can be salvaged and accessed externally by the user as mass storage device. A benefit over USB on the go storage expansion is uncompromised ergonomy. The usage of a memory card also protects the mobile phone's non-replaceable internal storage from weardown from heavy applications such as excessive camera usage and portable FTP server hosting over WiFi Direct. Due to the technical development of memory cards, users of existing mobile devices are able to expand their storage further and priceworthier with time.

Recent versions of major operating systems such as Windows Mobile and Android allow applications to run from microSD cards, creating possibilities for new usage models for SD cards in mobile computing markets, as well as clearing available internal storage space.

SD cards are not the most economical solution in devices that need only a small amount of non-volatile memory, such as station presets in small radios. They may also not present the best choice for applications that require higher storage capacities or speeds as provided by other flash card standards such as CompactFlash. These limitations may be addressed by evolving memory technologies, such as the new SD 7.0 specifications which allow storage capabilities of up to 128 TB.

Many personal computers of all types, including tablets and mobile phones, use SD cards, either through built-in slots or through an active electronic adapter. Adapters exist for the PC card, ExpressBus, USB, FireWire and the parallel printer port. Active adapters also let SD cards be used in devices designed for other formats, such as CompactFlash. The FlashPath adapter lets SD cards be used in a floppy disk drive.

Some devices such as the Samsung Galaxy Fit (2011) and Samsung Galaxy Note 8.0 (2013) have an SD card compartment located externally and accessible by hand, while it is located under the battery cover on other devices. More recent mobile phones use a pin-hole ejection system for the tray which houses both the memory card and SIM card.

Counterfeits

Commonly found on the market are mislabeled or counterfeit Secure Digital cards that report a fake capacity or run slower than labeled. Software tools exist to check and detect counterfeit products, and in some cases it is possible to repair these devices to remove the false capacity information and use its real storage limit.

Detection of counterfeit cards usually involves copying files with random data to the SD card until the card's capacity is reached, and copying them back. The files that were copied back can be tested either by comparing checksums (e.g. MD5), or trying to compress them. The latter approach leverages the fact that counterfeited cards let the user read back files, which then consist of easily compressible uniform data (for example, repeating 0xFFs).

Digital cameras

Secure Digital memory cards can be used in Sony XDCAM EX camcorders with an adapter.

Personal computers

Although many personal computers accommodate SD cards as an auxiliary storage device using a built-in slot, or can accommodate SD cards by means of a USB adapter, SD cards cannot be used as the primary hard disk through the onboard ATA controller, because none of the SD card variants support ATA signalling. Primary hard disk use requires a separate SD host controller or an SD-to-CompactFlash converter. However, on computers that support bootstrapping from a USB interface, an SD card in a USB adapter can be the boot disk, provided it contains an operating system that supports USB access once the bootstrap is complete.

In laptop and tablet computers, memory cards in an integrated memory card reader offer an ergonomical benefit over USB flash drives, as the latter sticks out of the device, and the user would need to be cautious not to bump it while transporting the device, which could damage the USB port. Memory cards have a unified shape and do not reserve a USB port when inserted into a computer's dedicated card slot.

Since late 2009, newer Apple computers with installed SD card readers have been able to boot in macOS from SD storage devices, when properly formatted to Mac OS Extended file format and the default partition table set to GUID Partition Table.

SD cards are increasing in usage and popularity among owners of vintage computers like Atari 8-bit computers. For example SIO2SD (SIO is an Atari port for connecting external devices) is used nowadays. Software for an 8-bit Atari may be included on one SD card that may have less than 4–8 GB of disk size (2019).

Embedded systems

In 2008, the SDA specified Embedded SD, "leverag well-known SD standards" to enable non-removable SD-style devices on printed circuit boards. However this standard was not adopted by the market while the MMC standard became the de facto standard for embedded systems. SanDisk provides such embedded memory components under the iNAND brand.

While some modern microcontrollers integrate SDIO hardware which uses the faster proprietary four-bit SD bus mode, almost all modern microcontrollers at least have SPI units that can interface to an SD card operating in the slower one-bit SPI bus mode. If not, SPI can also be emulated by bit banging (e.g. a SD card slot soldered to a Linksys WRT54G-TM router and wired to GPIO pins using DD-WRT's Linux kernel achieved only 1.6 Mbit/s throughput).

Music distribution

Prerecorded microSDs have been used to commercialize music under the brands slotMusic and slotRadio by SanDisk and MQS by Astell & Kern.

Technical details

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Physical size

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The SD card specification defines three physical sizes. The SD and SDHC families are available in all three sizes, but the SDXC and SDUC families are not available in the mini size, and the SDIO family is not available in the micro size. Smaller cards are usable in larger slots through use of a passive adapter.

Standard

• SD (SDSC), SDHC, SDXC, SDIO, SDUC
• 32 mm × 24 mm × 2.1 mm (1+17⁄64 in × 15⁄16 in × 5⁄64 in)
• 32 mm × 24 mm × 1.4 mm (1+17⁄64 in × 15⁄16 in × 1⁄16 in) (as thin as MMC) for Thin SD (rare)

MiniSD

• miniSD, miniSDHC, miniSDIO
• 21.5 mm × 20 mm × 1.4 mm (27⁄32 in × 25⁄32 in × 1⁄16 in)

microSD

The micro form factor is the smallest SD card format.

• microSD, microSDHC, microSDXC, microSDUC
• 15 mm × 11 mm × 1 mm (19⁄32 in × 7⁄16 in × 3⁄64 in)

Transfer modes

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Cards may support various combinations of the following bus types and transfer modes. The SPI bus mode and one-bit SD bus mode are mandatory for all SD families, as explained in the next section. Once the host device and the SD card negotiate a bus interface mode, the usage of the numbered pins is the same for all card sizes.

• SPI bus mode: Serial Peripheral Interface Bus is primarily used by embedded microcontrollers. This bus type supports only a 3.3-volt interface. This is the only bus type that does not require a host license.
• One-bit SD bus mode: Separate command and data channels and a proprietary transfer format.
• Four-bit SD bus mode: Uses extra pins plus some reassigned pins. This is the same protocol as the one-bit SD bus mode which uses one command and four data lines for faster data transfer. All SD cards support this mode. UHS-I and UHS-II require this bus type.
• Two differential lines SD UHS-II mode: Uses two low-voltage differential signaling interfaces to transfer commands and data. UHS-II cards include this interface in addition to the SD bus modes.

The physical interface comprises 9 pins, except that the miniSD card adds two unconnected pins in the center and the microSD card omits one of the two V_SS (Ground) pins.

Notes:

1. Direction is relative to card. I = Input, O = Output.
2. PP = Push-Pull logic, OD = Open-Drain logic.
3. S = Power Supply, NC = Not Connected (or logical high).

Interface

Command interface

SD cards and host devices initially communicate through a synchronous one-bit interface, where the host device provides a clock signal that strobes single bits in and out of the SD card. The host device thereby sends 48-bit commands and receives responses. The card can signal that a response will be delayed, but the host device can abort the dialogue.

Through issuing various commands, the host device can:

• Determine the type, memory capacity and capabilities of the SD card
• Command the card to use a different voltage, different clock speed, or advanced electrical interface
• Prepare the card to receive a block to write to the flash memory, or read and reply with the contents of a specified block.

The command interface is an extension of the MultiMediaCard (MMC) interface. SD cards dropped support for some of the commands in the MMC protocol, but added commands related to copy protection. By using only commands supported by both standards until determining the type of card inserted, a host device can accommodate both SD and MMC cards.

Electrical interface

All SD card families initially use a 3.3 volt electrical interface. On command, SDHC and SDXC cards can switch to 1.8 V operation.

At power-up or card insertion, the voltage on pin 1 selects either the Serial Peripheral Interface (SPI) bus or the SD bus. The SD bus starts in one-bit mode, but the host device may issue a command to switch to the four-bit mode, if the SD card supports it. For various card types, support for the four-bit SD bus is either optional or mandatory.

After determining that the SD card supports it, the host device can also command the SD card to switch to a higher transfer speed. Until determining the card's capabilities, the host device should not use a clock speed faster than 400 kHz. SD cards other than SDIO (see below) have a "Default Speed" clock rate of 25 MHz. The host device is not required to use the maximum clock speed that the card supports. It may operate at less than the maximum clock speed to conserve power. Between commands, the host device can stop the clock entirely.

MBR and FAT

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Most SD cards ship preformatted with one or more MBR partitions, where the first or only partition contains a file system. This lets them operate like the hard disk of a personal computer. Per the SD card specification, an SD card is formatted with MBR and the following file system:

• For SDSC cards:
  • Capacity of less than 32,680 logical sectors (smaller than 16 MB): FAT12 with partition type 01h and BPB 3.0 or EBPB 4.1
  • Capacity of 32,680 to 65,535 logical sectors (between 16 MB and 32 MB): FAT16 with partition type 04h and BPB 3.0 or EBPB 4.1
  • Capacity of at least 65,536 logical sectors (larger than 32 MB): FAT16B with partition type 06h and EBPB 4.1
• For SDHC cards:
  • Capacity of less than 16,450,560 logical sectors (smaller than 7.8 GB): FAT32 with partition type 0Bh and EBPB 7.1
  • Capacity of at least 16,450,560 logical sectors (larger than 7.8 GB): FAT32 with partition type 0Ch and EBPB 7.1
• For SDXC cards: exFAT with partition type 07h

Most consumer products that take an SD card expect that it is partitioned and formatted in this way. Universal support for FAT12, FAT16, FAT16B and FAT32 allows the use of SDSC and SDHC cards on most host computers with a compatible SD reader, to present the user with the familiar method of named files in a hierarchical directory tree.

On such SD cards, standard utility programs such as Mac OS X's "Disk Utility" or Windows' SCANDISK can be used to repair a corrupted filing system and sometimes recover deleted files. Defragmentation tools for FAT file systems may be used on such cards. The resulting consolidation of files may provide a marginal improvement in the time required to read or write the file, but not an improvement comparable to defragmentation of hard drives, where storing a file in multiple fragments requires additional physical and relatively slow, movement of a drive head. Moreover, defragmentation performs writes to the SD card that count against the card's rated lifespan. The write endurance of the physical memory is discussed in the article on flash memory; newer technology to increase the storage capacity of a card provides worse write endurance.

When reformatting an SD card with a capacity of at least 32 MB (65,536 logical sectors or more), but not more than 2 GB, FAT16B with partition type 06h and EBPB 4.1 is recommended if the card is for a consumer device. (FAT16B is also an option for 4 GB cards, but it requires the use of 64 KB clusters, which are not widely supported.) FAT16B does not support cards above 4 GB at all.

The SDXC specification mandates the use of Microsoft's proprietary exFAT file system, which sometimes requires appropriate drivers (e.g. exfat-utils/exfat-fuse on Linux).

Risks of reformatting

Reformatting an SD card with a different file system, or even with the same one, may make the card slower, or shorten its lifespan. Some cards use wear leveling, in which frequently modified blocks are mapped to different portions of memory at different times, and some wear-leveling algorithms are designed for the access patterns typical of FAT12, FAT16 or FAT32. In addition, the preformatted file system may use a cluster size that matches the erase region of the physical memory on the card; reformatting may change the cluster size and make writes less efficient. The SD Association provides freely downloadable SD Formatter software to overcome these problems for Windows and Mac OS X.

SD/SDHC/SDXC memory cards have a "Protected Area" on the card for the SD standard's security function. Neither standard formatters nor the SD Association formatter will erase it. The SD Association suggests that devices or software which use the SD security function may format it.

Power consumption

The power consumption of SD cards varies by its speed mode, manufacturer and model.

During transfer it may be in the range of 66–330 mW (20–100 mA at a supply voltage of 3.3 V). Specifications from TwinMOS Technologies list a maximum of 149 mW (45 mA) during transfer. Toshiba lists 264–330 mW (80–100 mA). Standby current is much lower, less than 0.2 mA for one 2006 microSD card. If there is data transfer for significant periods, battery life may be reduced noticeably; for reference, the capacity of smartphone batteries is typically around 6 Wh (Samsung Galaxy S2: 1650 mAh @ 3.7 V).

Modern UHS-II cards can consume up to 2.88 W, if the host device supports bus speed mode SDR104 or UHS-II. Minimum power consumption in the case of a UHS-II host is 720 mW.

Storage capacity and compatibilities

All SD cards let the host device determine how much information the card can hold, and the specification of each SD family gives the host device a guarantee of the maximum capacity a compliant card reports.

By the time the version 2.0 (SDHC) specification was completed in June 2006, vendors had already devised 2 GB and 4 GB SD cards, either as specified in Version 1.01, or by creatively reading Version 1.00. The resulting cards do not work correctly in some host devices.

SDSC cards above 1 GB

SD version 1.00 assumed 512 bytes per block. This permitted SDSC cards up to 4,096 × 512 × 512 B = 1 GB.

Version 1.01 let an SDSC card use a 4-bit field to indicate 1,024 or 2,048 bytes per block instead. Doing so enabled cards with 2 GB and 4 GB capacity, such as the Transcend 4 GB SD card, the Memorette 4 GB SD card and the Hoco 4 GB microSD card.

Storage capacity calculations

The format of the Card-Specific Data (CSD) register changed between version 1 (SDSC) and version 2.0 (which defines SDHC and SDXC).

Version 1

In version 1 of the SD specification, capacities up to 2 GB are calculated by combining fields of the CSD as follows:

Capacity = (C_SIZE + 1) × 2
where
 0 ≤ C_SIZE ≤ 4095,
 0 ≤ C_SIZE_MULT ≤ 7,
 READ_BL_LEN is 9 (for 512 bytes/sector) or 10 (for 1024 bytes/sector)

Later versions state (at Section 4.3.2) that a 2 GB SDSC card shall set its READ_BL_LEN (and WRITE_BL_LEN) to indicate 1,024 bytes, so that the above computation correctly reports the card's capacity, but that, for consistency, the host device shall not request (by CMD16) block lengths over 512 B.

Versions 2 and 3

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In the definition of SDHC cards in version 2.0, the C_SIZE portion of the CSD is 22 bits and it indicates the memory size in multiples of 512 KB (the C_SIZE_MULT field is removed and READ_BL_LEN is no longer used to compute capacity). Two bits that were formerly reserved now identify the card family: 0 is SDSC; 1 is SDHC or SDXC; 2 and 3 are reserved. Because of these redefinitions, older host devices do not correctly identify SDHC or SDXC cards nor their correct capacity.

• SDHC cards are restricted to reporting a capacity not over 32 GB.
• SDXC cards are allowed to use all 22 bits of the C_SIZE field. An SDHC card that did so (reported C_SIZE > 65,375 to indicate a capacity of over 32 GB) would violate the specification. A host device that relied on C_SIZE rather than the specification to determine the card's maximum capacity might support such a card, but the card might fail in other SDHC-compatible host devices.

Capacity is calculated thus:

Capacity = (C_SIZE + 1) × 524288
where for SDHC
 4112 ≤ C_SIZE ≤ 65375
 ≈2 GB ≤ Capacity ≤ ≈32 GB
where for SDXC
 65535 ≤ C_SIZE
 ≈32 GB ≤ Capacity ≤ 2 TB

Capacities above 4 GB can only be achieved by following version 2.0 or later versions. In addition, capacities equal to 4 GB must also do so to guarantee compatibility.

Openness of specification

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Like most memory card formats, SD is covered by numerous patents and trademarks. Excluding SDIO cards, royalties for SD card licenses are imposed for manufacture and sale of memory cards and host adapters (US$1,000/year plus membership at US$1,500/year)

Early versions of the SD specification were available under a non-disclosure agreement (NDA) prohibiting development of open-source drivers. However, the system was eventually reverse-engineered and free software drivers provided access to SD cards not using DRM. Subsequent to the release of most open-source drivers, the SDA provided a simplified version of the specification under a less restrictive license helping reduce some incompatibility issues.

Under a disclaimers agreement, the simplified specification released by the SDA in 2006 – as opposed to that of SD cards – was later extended to the physical layer, ASSD extensions, SDIO and SDIO Bluetooth Type-A.

The Simplified Specification is available.

Again, most of the information had already been discovered and Linux had a fully free driver for it. Still, building a chip conforming to this specification caused the One Laptop per Child project to claim "the first truly Open Source SD implementation, with no need to obtain an SDI license or sign NDAs to create SD drivers or applications."

The proprietary nature of the complete SD specification affects embedded systems, laptop computers and some desktop computers; many desktop computers do not have card slots, instead using USB-based card readers if necessary. These card readers present a standard USB mass storage interface to memory cards, thus separating the operating system from the details of the underlying SD interface. However, embedded systems (such as portable music players) usually gain direct access to SD cards and thus need complete programming information. Desktop card readers are themselves embedded systems; their manufacturers have usually paid the SDA for complete access to the SD specifications. Many notebook computers now include SD card readers not based on USB; device drivers for these essentially gain direct access to the SD card, as do embedded systems.

The SPI-bus interface mode is the only type that does not require a host license for accessing SD cards.

Data recovery

A malfunctioning SD card can be repaired using specialized equipment, as long as the middle part, containing the flash storage, is not physically damaged. The controller can in this way be circumvented. This might be harder or even impossible in the case of monolithic card, where the controller resides on the same physical die.

See also

• Comparison of memory cards
• Flash memory
• Microdrive
• Serial Peripheral Interface Bus (SPI)
• Universal Flash Storage

Footnotes

1. except where indicated otherwise, 1 MB equals one million bytes
2. ^ here, 1 TB = 1024 B
3. except where stated otherwise, in this article 1 TB = 1000 billion bytes
4. ^ here, 1 GB = 1 GiB = 2 B
5. This speed is achievable using DDR208 controller.
6. The necessary recording and playback speed class requirements may vary by device.
7. 1 KB = 1024 B
8. ^ See discussion about storage capacity and compatibilities.
9. ^ here, MB = 1024 B

References

1. ^ "4 Features and Benefits of a Micro SD Transflash Memory Card – Steve's Digicams". steves-digicams.com. Archived from the original on 17 January 2014. Retrieved 30 November 2020.
2. ^ "Advantages and Disadvantages of Memory Cards". Engadget. 11 October 2016. Archived from the original on 28 October 2020. Retrieved 30 November 2020.
3. "Matsushita Electric, SanDisk and Toshiba Agree to Join Forces to Develop and Promote Next Generation Secure Memory Card". DP Review. 24 August 1999. Archived from the original on 4 September 2019. Retrieved 23 February 2016.
4. "Welcome to SD-3C, LLC". SD-3C. 30 March 2015. Archived from the original on 10 September 2019. Retrieved 23 February 2016.
5. "Matsushita Electric, SanDisk and Toshiba to Form SD Association to Promote Next Generation SD Memory Card". Toshiba. 30 March 2015. Archived from the original on 1 January 2019. Retrieved 23 February 2016.
6. "Using SD Memory Cards is Easy". SD Association. 22 June 2010. Archived from the original on 29 October 2021. Retrieved 2 January 2014.
7. "Three Giants to develop new "Secure Memory Card"". DP review. Archived from the original on 4 September 2019. Retrieved 23 February 2016.
8. Andrews, Ben (25 October 2022). "Flash back: the history of the SD card, and why we think it deserves more love". Digital Photography Review. Retrieved 19 June 2024.
9. "Press Releases 17 July 2003". Toshiba. 17 July 2003. Archived from the original on 8 September 2010. Retrieved 22 August 2010.
10. The Odd History of the SD Logo, 21 January 2019, retrieved 25 October 2023
11. "What is SD Card". Bitwarsoft.com. 24 July 2020. Archived from the original on 9 July 2021. Retrieved 30 June 2021.
12. Corporation, Bonnier (27 August 2000). "Popular Science". Bonnier Corporation – via Google Books.
13. Corporation, Bonnier (27 May 2000). "Popular Science". Bonnier Corporation – via Google Books.
14. "256 and 512 MB MMC / SD cards".
15. SanDisk Introduces The World's Smallest Removable Flash Card For Mobile Phones-The miniSD Card Archived 2009-01-14 at the Wayback Machine SanDisk.com
16. "HD録画のカムコーダ、DVD-R内蔵ミニノート……会場で見かけた新製品". ITmedia NEWS. 22 March 2004. Archived from the original on 11 September 2024. Retrieved 12 February 2024.
17. Rojas, Peter (2 March 2004). "T-Flash: aka 'Yet Another Memory Card Format'". Engadget. Archived from the original on 2 May 2019. Retrieved 2 May 2019.
18. "SanDisk releases new memory cards". CNET. 24 May 2004. Archived from the original on 22 February 2024. Retrieved 12 February 2024.
19. "TransFlash becomes MicroSD". Archived from the original on 11 September 2024. Retrieved 3 February 2024.
20. ^ "SanDisk Reveals Tiny New Memory Cards for Phones". Phonescoop.com. 28 February 2004. Archived from the original on 22 July 2012. Retrieved 2 January 2014.
21. "CeBIT 2004: "Настраиваемся на волну будущего" | Статьи | Компьютерное Обозрение". ko.com.ua. Archived from the original on 11 September 2024. Retrieved 12 February 2024.
22. SanDisk Introduces 4 GB miniSDHC Flash Card for Mobile Phones Archived 2009-01-15 at the Wayback Machine SanDisk.com
23. "SDXC SIGNALS NEW GENERATION OF REMOVABLE MEMORY WITH UP TO 2 TERABYTES OF STORAGE" (PDF). sdcard.org. SD Association. Archived (PDF) from the original on 11 September 2024. Retrieved 30 December 2023.
24. "Capacity (SD/SDHC/SDXC/SDUC) | SD Association". sdcard.org. 11 December 2020. Archived from the original on 8 March 2022. Retrieved 8 March 2022.
25. "SanDisk and Sony to expand Memory Stick Pro and Memory Stick Micro formats". SanDisk. 7 January 2009. Archived from the original on 7 January 2010. Retrieved 22 August 2010.
26. Mook, Nate (8 January 2009). "SD Card, Memory Stick formats to reach 2 terabytes, but when?". Beta news. Archived from the original on 9 March 2024. Retrieved 22 January 2024.
27. "Pretec introduces world's first SDXC card". Digital Photography Review. 6 March 2009. Archived from the original on 21 August 2010. Retrieved 22 August 2010.
28. "Canon EOS Rebel T2i/550D Digital SLR Camera Review". The Digital Picture. Archived from the original on 11 February 2010. Retrieved 9 February 2010.
29. Ng, Jansen (24 November 2009). "Lack of Card Readers Holding Back SDXC Flash Memory Adoption". DailyTech. Archived from the original on 11 June 2007. Retrieved 22 December 2009.
30. Ng, Jansen (30 November 2009). "Lenovo, HP, Dell Integrating SDXC Readers in New 32nm Intel "Arrandale" Laptops". DailyTech. Archived from the original on 1 January 2015. Retrieved 22 December 2009.
31. Ng, Jansen (22 December 2009). "Toshiba Sampling First SDXC Flash Memory Cards". DailyTech. Archived from the original on 25 November 2010. Retrieved 22 December 2009.
32. "Toshiba's 64 GB SDXC card to finally go on sale (in Japan)". CrunchGear. Archived from the original on 1 July 2010. Retrieved 9 August 2010.
33. "Panasonic Introduces New 64 GB* and 48 GB* SDXC Memory Cards, Available Globally in February 2010". Panasonic. Archived from the original on 21 April 2010. Retrieved 9 August 2010.
34. "Sandisk ships its highest capacity sd card ever". SanDisk. 22 February 2010. Archived from the original on 13 November 2011. Retrieved 9 August 2010.
35. Conneally, Tim (16 March 2011). "Lexar ships 128 GB Class 10 SDXC card; March 2011". Betanews.com. Archived from the original on 11 November 2023. Retrieved 22 January 2024.
36. "SDXC/SDHC 433X Class 16 Card from Pretec". Pretec. 13 June 2011. Archived from the original on 29 November 2011. Retrieved 3 December 2010.
37. "First 64GB microSD Card Here; When Will Smartphones Support It?", Pocket now, 7 October 2017, archived from the original on 11 October 2011, retrieved 4 October 2011
38. "Kingmax flaunts world's first 64 GB microSD card", Engadget, 26 May 2011, archived from the original on 25 June 2017, retrieved 11 September 2024
39. ^ "For Journalists". .panasonic.com. 20 March 2013. Archived from the original on 26 May 2013. Retrieved 2 January 2014.
40. "microP2 Card | P2 Series | Broadcast and Professional AV". Pro-av.panasonic.net. Archived from the original on 7 January 2014. Retrieved 2 January 2014.
41. Lawler, Richard (15 April 2012). "Panasonic introduces new microP2 SD-sized storage at NAB 2012". Engadget.com. Archived from the original on 19 December 2013. Retrieved 2 January 2014.
42. Renée, V (23 March 2013). "Panasonic's New Smaller, Faster, and Lower-Cost MicroP2 Cards Coming in April, Starting at $250 « No Film School". Nofilmschool.com. Archived from the original on 29 December 2013. Retrieved 2 January 2014.
43. "Lexar Announces Industry's First 256 GB SDXC UHS-I Memory Card". Micron. Archived from the original on 29 January 2013. Retrieved 22 December 2012.
44. SanDisk. "SANDISK INTRODUCES WORLD'S HIGHEST CAPACITY microSDXC MEMORY CARD AT 128GB". sandisk.com.
45. "SanDisk introduces the first 200GB microSDXC card". SanDisk.com. 24 February 2014. Archived from the original on 1 September 2015. Retrieved 6 June 2016.
46. SanDisk. "SanDisk Premieres World's Highest Capacity SD Card for High Performance Video and Photo Capture". sandisk.com. Archived from the original on 18 January 2017. Retrieved 20 September 2016.
47. "Samsung Electronics Introduces the EVO Plus 256 GB MicroSD Card, with the Highest Capacity in its Class". news.samsung.com. 10 May 2016. Archived from the original on 8 August 2016. Retrieved 6 June 2016.
48. SanDisk. "Western Digital Demonstrates Prototype of the World's First 1Terabyte SDXC Card". sandisk.com. Archived from the original on 18 January 2017. Retrieved 20 September 2016.
49. Shilov, Anton. "Western Digital Launches SanDisk Ultra microSD Card with 400 GB Capacity". Archived from the original on 31 August 2017. Retrieved 11 September 2024.
50. Integral Memory (22 January 2018). "Integral Memory's new 512GB microSD card is the biggest microSD card yet". theverge.com. Archived from the original on 12 June 2018. Retrieved 10 June 2018.
51. Kingston. "Kingston Digital Announces New 'Canvas' Series of Flash Cards". Kingston Technology Europe Co LLP. Archived from the original on 21 November 2018. Retrieved 19 November 2018.
52. "SanDisk's 1TB microSD card is now available". theverge.com. 15 May 2019. Archived from the original on 17 June 2020. Retrieved 19 December 2019.
53. "Western Digital Showcases New Super Speeds and Massive Capacities for M&E Workflows at NAB 2024". westerndigital.com. 11 April 2024. Archived from the original on 11 September 2024.
54. ^ "Capacity". SD Association. Archived from the original on 20 May 2020. Retrieved 8 December 2011.
55. ^ "Using SDXC". SD Association. Archived from the original on 10 October 2014. Retrieved 8 December 2011.
56. "SDIO". SD Association. Archived from the original on 20 May 2020. Retrieved 8 December 2011.
57. "Capacity (SD/SDHC/SDXC/SDUC) – SD Association". sdcard.org. Archived from the original on 28 February 2019. Retrieved 15 February 2019.
58. ^ "Capacity (SD/SDHC/SDXC/SDUC) | SD Association". sdcard.org. 11 December 2020. Archived from the original on 11 September 2024. Retrieved 3 May 2023.
59. What are SDHC, miniSDHC, and microSDHC? SanDisk. Archived September 16, 2008, at the Wayback Machine
60. Bus Speed (Default Speed/ High Speed/ UHS) Archived 2016-10-04 at the Wayback Machine SDcard.
61. ^ About Compatibility with Host Devices Archived 2011-11-21 at the Wayback Machine SD Association.
62. What's new in Firmware 2.41 Beta (for COWON D2) Archived 2011-08-28 at the Wayback Machine JetAudio.
63. "934428 – Hotfix for Windows XP that adds support for SDHC cards that have a capacity of more than 4 GB". Support. Microsoft. 15 February 2008. Archived from the original on 3 January 2010. Retrieved 22 August 2010.
64. "939772 – Some Secure Digital (SD) cards may not be recognized in Windows Vista". Support. Microsoft. 15 May 2008. Archived from the original on 9 February 2010. Retrieved 22 August 2010.
65. "949126 – A Secure Digital High Capacity (SDHC) card is not recognized on a Windows Vista Service Pack 1-based computer". Support. Microsoft. 21 February 2008. Archived from the original on 9 January 2010. Retrieved 22 August 2010.
66. "Capacity (SD/SDHC/SDXC)". SD Association. Archived from the original on 21 November 2011. Retrieved 20 March 2017.
67. ^ "Bus Speed (Default Speed/ High Speed/ UHS)". SD Association. Archived from the original on 4 October 2016. Retrieved 20 March 2017.
68. "Lexar Professional 1066x microSDXC UHS-I Card SILVER Series". Lexar. Archived from the original on 10 April 2021. Retrieved 10 April 2021.
69. "SanDisk Extreme PRO SDHC And SDXC UHS-I Card". shop.westerndigital.com. Archived from the original on 10 April 2021. Retrieved 10 April 2021.
70. "Canvas Go! Plus Class 10 SD Cards – UHS-I, U3, V30 – 64 GB–512 GB". Kingston Technology Company. Archived from the original on 11 October 2021. Retrieved 10 April 2021.
71. "Canvas Go! Plus Class 10 microSD Cards – V30, A2 – 64 GB–512 GB". Kingston Technology Company. Retrieved 10 April 2021.
72. ^ "NEW SD ASSOCIATION VIDEO SPEED CLASS SUPPORTS 8K AND MULTI-FILE VIDEO RECORDING" (PDF). SD Association. 26 February 2016. Archived from the original (PDF) on 7 March 2016. Retrieved 3 March 2016.
73. Shilov, Anton (1 March 2016). "SD Association Announces SD 5.0 Specification: SD Cards For UHD and 360° Video Capture". Anand Tech. Archived from the original on 3 March 2016. Retrieved 3 March 2016.
74. ^ "Video Speed Class: The new capture protocol of SD 5.0" (PDF). SD Association. February 2016. Archived from the original (PDF) on 23 December 2016. Retrieved 3 March 2016.
75. Chaundy, Fabian (26 February 2016). "New Video Speed Class for SD Cards". cinema5D. Archived from the original on 7 March 2016. Retrieved 3 March 2016.
76. "SD Express Cards with PCIe and NVMeTM Interfaces" (PDF). SD Association. June 2018. Archived from the original (PDF) on 12 November 2020. Retrieved 21 November 2018.
77. "Notable Changes in Windows Vista Service Pack 1". TechNet. Microsoft Docs. 25 July 2008. Archived from the original on 7 November 2021. Retrieved 7 November 2021.
78. "About the SD and SDXC card slots". Apple Inc. 3 May 2011. Archived from the original on 3 September 2011. Retrieved 5 September 2011.
79. "Apple released exFAT support in OS X 10.6.5 update". Tuxera.com. 22 November 2010. Archived from the original on 13 May 2012. Retrieved 4 January 2012.
80. "Description of the exFAT file system driver update package". Microsoft. 8 October 2011. Archived from the original on 11 May 2015. Retrieved 27 November 2015.
81. "The Initial exFAT Driver Queued For Introduction With The Linux 5.4 Kernel". phoronix.com. 30 August 2019. Archived from the original on 18 December 2019. Retrieved 5 February 2020.
82. "exFAT for BSD and Linux systems from Google Code". Archived from the original on 11 January 2014. Retrieved 2 January 2014.
83. deKay (15 January 2015). "Updated: How to upgrade your 3DS SD card, to 64GB and beyond". Lofi-Gaming. Archived from the original on 21 December 2018. Retrieved 21 December 2018.
84. List, Jenny (29 November 2017). "Ask Hackaday: How On Earth Can A 2004 MP3 Player Read An SDXC Card?". Hackaday. Archived from the original on 21 December 2018. Retrieved 21 December 2018.
85. Sims, Gary (9 May 2016). "High capacity microSD cards and Android – Gary explains". Android Authority. Archived from the original on 22 November 2018. Retrieved 21 December 2018.
86. "SD Formatter 4.0 for SD/SDHC/SDXC – SD Association". Sdcard.org. Archived from the original on 7 February 2014. Retrieved 2 January 2014.
87. ^ Kim, H; Agrawal, N; Ungureanu, C (30 January 2012), Revisiting Storage for Smartphones (PDF), America: NEC Laboratories, table 3, archived (PDF) from the original on 10 October 2012, retrieved 27 December 2012, Speed class considered irrelevant: our benchmarking reveals that the "speed class" marking on SD cards is not necessarily indicative of application performance; although the class rating is meant for sequential performance, we find several cases in which higher-grade SD cards performed worse than lower-grade ones overall.
88. ^ Lui, Gough (16 January 2014). "SD Card Sequential, Medium & Small Block Performance Round-Up". Gough's techzone. Archived from the original on 8 December 2015. Retrieved 29 November 2015. Variations in 4k small block performance saw a difference of approximately 300-fold between the fastest and slowest cards. Distressingly, many of the tested cards were mediocre to poor on that metric, which may explain why running updates on Linux running off SD cards can take a very long time.
89. "Raspberry Pi forum: SD card benchmarks". Archived from the original on 13 August 2014. Retrieved 12 August 2014.
90. ^ "SD Speed Class". SDCard.org. Archived from the original on 21 December 2020. Retrieved 13 November 2013.
91. "Bus Speed (Default Speed/High Speed/UHS/SD Express)". SD card. SD Association. Archived from the original on 4 October 2016. Retrieved 18 April 2020.
92. ^ "Bus Speed (Default Speed/ High Speed/ UHS)". SD card. SD Association. Archived from the original on 4 October 2016. Retrieved 13 November 2013.
93. "SD cards branded with an upper-case 'I' are faster, yo". Engadget. 24 June 2010. Archived from the original on 28 August 2010. Retrieved 22 August 2010.
94. Rigg, Jamie (16 July 2013). "Toshiba's Exceria Pro SDHC cards claim 'world's fastest' write speeds of 240 MB per second". Engadget. Archived from the original on 19 December 2013. Retrieved 2 January 2014.
95. "SD Standard Overview". SD Association. 11 December 2020. Retrieved 19 June 2023.
96. ^ "SD Part 1, Physical Layer Simplified Specification, Version 3.01" (PDF). SD Association. 18 May 2010. Archived from the original (PDF) on 5 December 2013. Retrieved 25 November 2013.
97. "SanDisk Extreme microSDXC datasheet" (PDF). Western Digital. Archived (PDF) from the original on 8 January 2021. Retrieved 4 February 2021.
98. "GL3232". Genesys Logic. Archived from the original on 21 September 2020. Retrieved 4 February 2021.
99. "Association Triples Speeds with UHS-II" (PDF). SD Card. 5 January 2011. Archived from the original (PDF) on 21 March 2011. Retrieved 9 August 2011.
100. "UHS-II camera list". memorycard-lab.com. Retrieved 19 January 2024.
101. "SD Association Doubles Bus Interface Speeds with UHS-III" (PDF). 23 February 2017. Archived from the original (PDF) on 24 February 2017. Retrieved 23 February 2017.
102. "Introducing SD Express". Card wave services. July 2018. Archived from the original on 23 December 2018. Retrieved 23 December 2018.
103. "Thunderclap: Exploring Vulnerabilities in Operating System IOMMU Protection via DMA from Untrustworthy Peripherals". NDSS Symposium. Archived from the original on 6 August 2019. Retrieved 6 August 2019.
104. "SDExpress Delivers New Gigabtye Speeds For SDMemory Cards" (PDF). SD card (Press release). SD association. Archived (PDF) from the original on 20 May 2020. Retrieved 19 May 2020.
105. "sd 9.0" (PDF). Archived (PDF) from the original on 2 August 2024. Retrieved 31 July 2024.
106. ^ "New SD Express Specifications Introduce New Speed Classes and Next-Level Performance Features | SD Association". www.sdcard.org. 27 October 2023. Archived from the original on 1 April 2024. Retrieved 1 April 2024.
107. Gartenberg, Chain (25 February 2019). "Memory cards are about to get much faster with new microSD Express spec". The Verge. Archived from the original on 15 March 2019. Retrieved 18 March 2019.
108. Henchman, Mark (25 February 2019). "The microSD Express standard combines PCI Express speeds, microSD convenience". Archived from the original on 8 August 2019. Retrieved 18 March 2019.
109. "Bus Speed (Default Speed/High Speed/UHS/SD Express)". SD card. SD Association. Archived from the original on 4 October 2016. Retrieved 15 February 2019.
110. "SD Express Cards with Pie and Name Interfaces" (PDF). SD Association: 9. June 2018. Archived from the original (PDF) on 12 November 2020. Retrieved 27 June 2018.
111. ^ "Speed Class Standards for Video Recording – SD Association". sdcard.org. 11 December 2020. Archived from the original on 7 April 2016. Retrieved 28 April 2016.
112. "SD Standards Brochure 2017" (PDF). Archived from the original (PDF) on 30 March 2017. Retrieved 29 March 2017.
113. "NEW SDXC AND SDHC MEMORY CARDS SUPPORT 4K2K VIDEO" (PDF). SD Association. Archived (PDF) from the original on 13 November 2013. Retrieved 13 November 2013.
114. "Speed Class". SD Association. Archived from the original on 28 February 2019. Retrieved 15 February 2019.
115. ""Application Performance Class: The new class of performance for applications on SD memory cards (SD 5.1)" (PDF). sdcard.org. November 2016. Archived (PDF) from the original on 23 November 2016. Retrieved 11 September 2024.
116. hominoid. "Linux Supports A2 SDcards now! – ODROID". ODROID by Hardkernel. ODROID. Archived from the original on 25 August 2023. Retrieved 25 August 2023.
117. "Application Performance Class – SD Association". sdcard.org. Archived from the original on 28 February 2019. Retrieved 15 February 2019.
118. "Flash Memory Cards and X-Speed Ratings". Kingston. Archived from the original on 2 July 2017. Retrieved 5 August 2017.
119. By (19 January 2014). "The Tiniest SD Card Locker". Hackaday. Retrieved 20 January 2023.
120. US patent 7827370 
121. "Simplified Specifications – SD Association, version 3.10, Part 1, Physical Layer, section 4.3.6" Write Protect Management"". sdcard.org. Archived from the original on 11 April 2019. Retrieved 11 April 2019.
122. "Windows Phone 7 – Microsoft Support". support.microsoft.com. Archived from the original on 3 May 2016. Retrieved 22 January 2023.
123. "Windows Phone 7's microSD mess: the full story (and how Nokia can help you out of it)". Engadget. 17 November 2010. Archived from the original on 8 August 2019. Retrieved 13 October 2019.
124. "Activating New Mobile Services and Business Models with smartSD Memory cards" (PDF). SD Association. November 2014. Archived from the original (PDF) on 23 December 2016. Retrieved 2 August 2017.
125. Clark, Sarah (11 November 2009). "DeviceFidelity launches low cost microSD-based NFC solution". nfcw.com. Archived from the original on 4 March 2021. Retrieved 28 July 2021.
126. "DeviceFidelity rolls out microSD payment tool". SecureIDNews. 10 November 2009. Archived from the original on 8 May 2021. Retrieved 28 July 2021.
127. "Visa and DeviceFidelity Collaborate to Accelerate Adoption of Mobile Contactless Payments". visa.com. 15 February 2010. Archived from the original on 19 September 2015. Retrieved 28 July 2021.
128. "In2Pay is the name of Visa and DeviceFidelity's money-grubbing iPhone case". Engadget. 18 May 2010. Archived from the original on 26 January 2021. Retrieved 28 July 2021.
129. "Device Fidelity's Amitaabh Mohortra Speaks about their micro NFC device for almost any phone". youtube.com. 26 October 2013. Archived from the original on 29 October 2021. Retrieved 28 July 2021.
130. Clark, Mike (23 September 2010). "DeviceFidelity adds NFC microSD support for iPhone 4". nfcw.com. Archived from the original on 19 January 2021. Retrieved 28 July 2021.
131. "smartSD Memory Cards". SD Association. Archived from the original on 8 July 2015. Retrieved 23 February 2016.
132. "MicroSD Vendor Announces Taiwanese M-Payment Trial Using HTC NFC Phones". NFC Times. Archived from the original on 27 April 2016. Retrieved 23 February 2016.
133. Hudson, Andrew (10 December 2012). "DeviceFidelity's Good Vault provides identity and access solution for iOS". SecureIDNews. Archived from the original on 23 October 2021. Retrieved 28 July 2021.
134. "Datacard Group, DeviceFidelity and U.S. Bank Announce New Smart Card and Mobile Payment Program" (Press release). Datacard Group. 14 January 2013. Archived from the original on 20 August 2021. Retrieved 28 July 2021 – via Businesswire.
135. Clark, Sarah (19 August 2010). "Bank of America to run NFC payments trial in New York". nfcw.com. Archived from the original on 25 January 2021. Retrieved 28 July 2021.
136. "Wells Fargo to Roll Out Mobile Payments Pilot; Visa Demonstrating Capability at CARTES 2010 | Business Wire". Archived from the original on 14 October 2020. Retrieved 14 October 2020.
137. "DeviceFidelity and SpringCard Launch moneto, the World's First Multi-Platform Mobile Wallet for iPhone and Android at CES" (Press release). DeviceFidelity. 10 January 2012. Archived from the original on 13 January 2012. Retrieved 28 July 2021 – via Cision.
138. Clark, Sarah (11 September 2012). "Moneto to bring NFC payments to Europe". nfcw.com. Archived from the original on 25 January 2021. Retrieved 28 July 2021.
139. "Garanti Bank deploys NFC services on microSD". RFID Ready. Archived from the original on 2 February 2017. Retrieved 23 February 2016.
140. "DeviceFidelity launches new range of NFC microSD devices". NFC World+. 31 October 2012. Archived from the original on 20 April 2016. Retrieved 23 February 2016.
141. "iPhone Voice Encryption from KoolSpan and DeviceFidelity". koolspan.com. 11 March 2013. Archived from the original on 27 January 2021. Retrieved 28 July 2021.
142. Corum, Chris (14 September 2011). "Arizona students first to trial mobile phones with NFC for door access". CR80 News. Archived from the original on 6 November 2021. Retrieved 28 July 2021.
143. "Case Study: Mobile Access Pilot at Arizona State University". youtube.com. 14 October 2011. Archived from the original on 29 October 2021. Retrieved 28 July 2021.
144. "Eye-Fi". Archived from the original on 26 August 2010. Retrieved 22 August 2010.
145. Robson, Wayde (22 September 2008). "AudioHolics". AudioHolics. Archived from the original on 2 June 2013. Retrieved 2 January 2014.
146. "slotRadio". SanDisk. Archived from the original on 24 November 2011. Retrieved 27 November 2011.
147. "SanDisk Ultra II SD Plus USB/SD card", The Register, UK, 25 July 2005, archived from the original on 8 August 2019, retrieved 11 September 2024
148. "A-DATA Super Info SD Card 512MB". Tech power up. 20 February 2007. Archived from the original on 18 May 2012. Retrieved 30 December 2011.
149. "Simplified Version of SDIO CARD SPEC". SD Association. Archived from the original on 15 April 2015. Retrieved 9 December 2011.
150. "Understanding Life Expectancy of Flash Storage". ni.com. 23 July 2020. Archived from the original on 13 September 2023. Retrieved 30 November 2020.
151. "12 Advantages & Disadvantages of Using SD Card in Smartphone". Data Recovery Blog. 23 November 2017. Archived from the original on 30 November 2020. Retrieved 30 November 2020.
152. Ali, Mudassar (27 November 2018). "Benefits of Using an SD Card". Medium. Archived from the original on 30 November 2020. Retrieved 30 November 2020.
153. "Inside Marshmallow: Adoptable storage". Android Central. 15 November 2015. Archived from the original on 21 February 2016. Retrieved 23 February 2016.
154. "Speed Class Standards for Video Recording". SD Association. Archived from the original on 7 April 2016. Retrieved 21 November 2018.
155. bunnie. "On MicroSD Problems". bunniestudios.com. Archived from the original on 11 September 2024. Retrieved 22 January 2024.
156. Schnurer, Georg (28 February 2007). "Gefälschte SD-Karten" [Fake SD-cards] (in German). Heise mobile – c't magazin für computertechnik. Archived from the original on 23 June 2013. Retrieved 7 June 2013.
157. Feddern, Boi (18 March 2013). "Smartphones wählerisch bei microSDHC-Karten" (in German). Heise mobile – c't magazin für computertechnik. Archived from the original on 1 January 2019. Retrieved 9 June 2013.
158. "H2testw heise Download" (in German). Archived from the original on 26 November 2016. Retrieved 26 November 2016.
159. "F3 by Digirati". Archived from the original on 24 November 2016. Retrieved 26 November 2016.
160. "Определение модели контроллера и памяти флешки" [Detecting controller model and memory type of flash drive] (in Russian). usbdev.ru. 20 February 2013. Archived from the original on 24 June 2023. Retrieved 6 January 2018.
161. "About VID PID Repairing Counterfeit Flash Drives – Steps To Succeed" Archived 2011-01-09 at the Wayback Machine, fixfakeflash.wordpress.com, retrieved November 16, 2010
162. "MEAD-SD01 SDHC card adapter (Sony)". Pro.sony.com. Archived from the original on 29 June 2017. Retrieved 2 January 2014.
163. "TS-7800 Embedded". Embeddedarm.com. Archived from the original on 15 February 2015. Retrieved 22 August 2010.
164. "About the SD and SDXC card slot". Support.apple.com. 8 June 2013. Archived from the original on 3 September 2011. Retrieved 13 November 2013.
165. "SIO2SD for 8-bit Atari". 9 May 2016. Archived from the original on 13 October 2019. Retrieved 13 October 2019.
166. "Embedded SD". SD Association. Archived from the original on 21 November 2011. Retrieved 30 November 2011.
167. "iNAND Embedded Flash Drives". SanDisk. Archived from the original on 25 December 2011. Retrieved 30 November 2011.
168. "Linksys WRT54G-TM SD/MMC mod – DD-WRT Wiki". Dd-wrt.com. 22 February 2010. Archived from the original on 1 September 2010. Retrieved 22 August 2010.
169. "About". SD Association. Archived from the original on 21 November 2011. Retrieved 2 May 2011.
170. "SD Part 1, Physical Layer Simplified Specification, Version 4.10" (PDF). Archived from the original (PDF) on 2 December 2013. Retrieved 2 January 2014.
171. ^ SD Memory Card Specifications – PART 2 FILE SYSTEM SPECIFICATION – Version 1.0. 1.0. SD Group, Matsushita Electric Industrial Co., Ltd. (MEI), SanDisk Corporation, Toshiba Corporation. February 2000.
172. Fragmentation and Speed, SD Card, 11 December 2020, archived from the original on 3 June 2018, retrieved 21 November 2011
173. "SDXC memory cards promise 2 TB of storage, 300 MBps transfer". Engadget. 7 January 2009. Archived from the original on 11 February 2010. Retrieved 22 August 2010.
174. "Optimizing Linux with cheap flash drives". Linux Weekly News. Archived from the original on 7 October 2013. Retrieved 11 April 2011.
175. ^ SD Formatter 3.1 for SD/SDHC/SDXC Archived 2021-02-07 at the Wayback Machine, SD Association
176. "microSD & microSDHC Cards", Memory Solutions, Toshiba, archived from the original on 18 August 2013, retrieved 27 February 2011
177. Micro SD specification (PDF), DTT, archived from the original (PDF) on 7 February 2013
178. "SD Specifications Version 4.10", 3.10.5 – Summary of Bus Speed Mode for UHS-II Card (PDF), SD Association, archived (PDF) from the original on 29 October 2013, retrieved 1 September 2013
179. "A look into how SDHC will affect the future Nand Flash market", DRAMeXchange, December 2006, archived from the original on 4 February 2008, retrieved 8 March 2007
180. "SD Compatibility", Card speed – Card Readers and Memory Cards, HJ Reggel, 1 December 2006, archived from the original on 25 January 2007, retrieved 31 January 2007
181. "WinXP SP3 cannot read 4GB SD card in multicard reader". Egg head cafe. Archived from the original on 30 July 2012. Retrieved 22 August 2010.
182. "Sharp Linux PDA promotes the use of proprietary SD card, but more open MMC works just fine". Linux.com. 14 June 2007. Archived from the original on 15 December 2010. Retrieved 22 August 2010.
183. Simplified Specification Agreement Archived 2008-10-28 at the Wayback Machine from the SDA's website
184. "Simplified Specification" (PDF). Archived (PDF) from the original on 18 December 2020. Retrieved 31 July 2024.
185. "OLPC mailing list archive". Mailman.laptop.org. Archived from the original on 12 April 2011. Retrieved 22 August 2010.
186. team, ACELab. "PC-3000 Flash. How to recover data from a monolith (microSD card)". Archived from the original on 13 October 2019. Retrieved 13 October 2019.
187. "New adapters for monolithic devices!". 21 September 2017. Archived from the original on 4 February 2018. Retrieved 11 September 2024.

External links

• SD Association Official Site
  • SD simplified specifications
  • SD Memory Card Formatter
• How to Use MMC/SDC elm-chan.org, December 26, 2019
• Optimizing Linux with cheap flash drives lwn.net
• Flash memory card: design, and List of cards and their characteristics linaro
• Independent SD Card Speed Tests
  • Types of Memory Cards and Sizes

v t e Memory cards
Main articles	Memory card reader Comparison of memory cards
Types	CompactFlash (CF, CFast, CFexpress) Express Card JEIDA MultiMediaCard (MMC) Memory Stick (MS, MS-PRO, MS-PRO HG, MS-XC) miCard Microdrive (MD) MiniCard NT Card P2 (MicroP2) PC Card (PCMCIA, CardBus, CardBay) Secure Digital (SDSC, SDHC, SDXC) SmartMedia (SM) SxS Universal Flash Storage (UFS) xD-Picture XQD

• Computer-related introductions in 1999
• Japanese inventions
• Solid-state computer storage media