MultiMediaCard (MMC) – SanDisk and Siemens NAND memory card for phones and smaller devices

Ten years after releasing the CompactFlash card and watching it become very successful, SanDisk had a go at repeating the trick, this time in collaboration with German company Siemens, releasing the MultiMediaCard (MMC). This was designed to take over from CompactFlash in most markets but also reach newer, smaller devices that the CF format is simply too big to fit, such as mobile phones, smartphones and PDAs. An MMC card is about the size of a postage stamp whereas a CF card is closer to a book of matches. One disadvantage of the form factor is that it is possible to insert an MMC card into a card reader slot the wrong way round. As the pins won’t connect there won’t be any damage, but it can be frustrating. The size reduction was made possible by the adoption of NAND flash memory developed by Toshiba and introduced in their SmartMedia card format in 1995. NAND flash memory allows greater storage densities, is cheaper to make and the data states are retained for longer than NOR flash memory, the method used by CF. NAND flash memory also has to be written to and erased in block mode, rather than bit-by-bit. This property is a disadvantage for directly accessing memory, as you do with a PC’s RAM, but makes it a good match for emulating secondary storage such as hard disks or optical disks. MMC came on the market in 1997 and the available memory sizes have constantly increased since then, although not to the same extent as cards that are available in CF form. There is a theoretical limit of...

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