MicroSD removable miniaturized Secure Digital flash memory SD cards were originally named T-Flash or TF, abbreviations of TransFlash.
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37 Facts About SD cards
2.
TransFlash and microSD cards are functionally identical allowing either to operate in devices made for the other.
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3.
Since 2008, miniSD cards are no longer produced, due to market domination of the even smaller microSD cards.
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4.
Storage density of memory SD cards has increased significantly throughout the 2010s decade, 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.
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5.
SDXC SD cards are formatted with the exFAT filesystem by default.
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6.
The SD cards are essentially full-size SDHC or SDXC UHS-II SD cards, rated at UHS Speed Class U1.
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7.
Panasonic MicroP2 SD cards shipped in March 2013 and were the first UHS-II compliant products on market; initial offer includes a 32GB SDHC card and a 64GB SDXC card.
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8.
Full-size SD cards do not fit into the slimmer MMC slots, and other issues affect the ability to use one format in a host device designed for the other.
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9.
The major compatibility issues between SDHC and SDSC SD cards are the redefinition of the Card-Specific Data register in version 2.
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10.
SDXC and SDUC SD cards are normally formatted using the exFAT file system, thereby limiting their use to a limited set of operating systems.
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11.
However, SDXC SD cards can be reformatted to use any file system, alleviating the restrictions associated with exFAT availability.
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12.
Except for the change of file system, SDXC SD cards are mostly backward compatible with SDHC readers, and many SDHC host devices can use SDXC SD cards if they are first reformatted to the FAT32 file system.
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13.
The microSD Express SD cards offer PCI Express and NVMe interfaces, as the June 2018 SD Express release did, alongside the legacy microSD interface for continued backwards compatibility.
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14.
The SDA released visual marks to denote microSD Express memory SD cards to make matching the card and device easier for optimal device performance.
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15.
A2 class SD cards require host driver support as they use command queuing and write caching to achieve their higher speeds.
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16.
Windows Phone 7 devices use SD cards designed for access only by the phone manufacturer or mobile provider.
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17.
Various implementations of smartSD cards have been done for payment applications and secured authentication.
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18.
SDIO SD cards are only fully functional in host devices designed to support their input-output functions.
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19.
Low-Speed SDIO SD cards are allowed to support the four-bit SD bus; Full-Speed SDIO SD cards are required to support the four-bit SD bus.
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20.
The host device would broadcast commands to all SD cards and identify the card to respond to the command using its unique serial number.
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21.
In practice, SD cards are rarely ganged together because open-collector operation has problems at high speeds and increases power consumption.
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22.
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.
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23.
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.
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24.
Active adapters let SD cards be used in devices designed for other formats, such as CompactFlash.
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25.
Detection of counterfeit SD cards usually involves copying files with random data to the SD card until the card's capacity is reached, and copying them back.
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26.
The latter approach leverages the fact that counterfeited SD cards let the user read back files, which then consist of easily compressible uniform data.
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28.
Memory SD cards have a unified shape and do not reserve a USB port when inserted into a computer's dedicated card slot.
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29.
SD cards are increasing in usage and popularity among owners of vintage computers like 8-bit Atari.
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30.
Smaller SD cards are usable in larger slots through use of a passive adapter.
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31.
SD cards dropped support for some of the commands in the MMC protocol, but added commands related to copy protection.
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32.
Some SD 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.
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33.
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.
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34.
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.
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35.
All SD cards can be accessed freely using the well-documented SPI bus.
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36.
XD SD cards are simply 18-pin NAND flash chips in a special package and support the standard command set for raw NAND flash access.
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37.
The consortium that licenses xD SD cards has not released any technical information to the public.
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