du kan kigge forbi den her side .. det er på engelsk :)
http://en.wikipedia.org/wiki/Secure_Digital_CardThe Multimedia Card (MMC) is a flash memory memory card standard. Unveiled in 1997 by Siemens AG and SanDisk, it is based on Toshiba's NAND-based flash memory, and is therefore much smaller than earlier systems based on Intel NOR-based memory such as Compact Flash. MMC is about the size of a postage stamp: 24mm x 32mm x 1.5mm. MMC originally used a 1-bit serial interface, but newer versions of the specification allow transfers of 4 or sometimes even 8 bits at a time. They have been more or less superseded by Secure Digital cards, but still see significant use because MMC cards can be used in any device which supports SD cards.
Typically, an MMC card is used as storage media for a portable device, in a form that can easily be removed for access by a PC. For example, a digital camera would use an MMC card for storing image files. With an MMC reader (typically a small box that connects via USB or some other serial connection), a user could copy the pictures taken with the digital camera off to his or her computer. Modern computers, both laptops and desktops, often have SD slots, which can read MMC cards.
MMC cards are currently available in sizes up to and including 2 GB, and are used in almost every context in which memory cards are used, like cell phones, mp3 players, digital cameras, and PDAs. Since the introduction of Secure Digital few companies build MMC slots into their devices, but the slightly-thinner, pin-compatible MMC cards can be used in any device that supports SD cards. A handful of companies, most notably Nokia, still support MMC exclusively, however.
Secure Digital (SD) is a flash memory memory card format. It is used in portable devices, including digital cameras and handheld computers. SD cards are based on the older Multi Media Card (MMC) format, but are physically slightly thicker and boast higher data transfer rates, an optional lock switch on the side to prevent accidental overwriting, and (little-used) DRM features. SD cards measure 32 mm by 24 mm by 2.1 mm. There are two main types available, ones that run at regular speeds, and high-speed cards that have higher data transfer rates. Some digital cameras require high-speed cards to record video smoothly or capture multiple still photographs in rapid succession.
Devices with SD slots can use the thinner MMC cards, but SD cards will not fit into the thinner MMC slots. SD cards can be used directly in CompactFlash or PC Card slots with an adapter. MiniSD and MicroSD cards can be used directly in SD slots with an adapter. There are some SD cards that have a USB connector built in for dual-purpose use, and there are readers which allow SD cards to be accessed via many connectivity ports such as USB, FireWire, and the common parallel port. SD cards can also be accessed via a floppy disk drive with a FlashPath adapter.
