xD cardxD-Picture Card overview
Extreme Digital (xD) picture
cards are based on
Flash technology. In fact xD card is a NAND flash
chip embedded in plastic. Its main use is in digital cameras. Olympus and Fujifilm launched these cards in the market in 2002. Therefore these cards are used in Fujifilm digital cameras and MP3 player, and Olympus digital cameras and voice recorders. Olympus and Fujifilm own the complete pecifications of an xD card. Now Lexer, Kodak, and SanDisk also sell xD cards.
xD card Form factors
The weight of a standard xD card is 2.8 grams in a
form factorUSB cable. xD card readers are also available. It can also be inserted in a
PCMCIA,
Compact Flash, and
Smart media readers through an xD adapter.
xD Card types
Extreme Digital (xD) cards can be categorized inthree ways: standard, Type M, and Type H. standard xD cards were the first generation offering capcity ranging 32 MBs to 512 MBs. Then Type M cards were launched with larger capacities ranging 256 MBs to 2 GB.
Though type M cards offer more capcity but they suffer from very slow read and write operations. To overcome type M effecincy type H xD cards were launched with three times faster transfer (read / wite) speed. But type H xD cards are avaialble in 512 MB and 2 GB of capacities.
xD card and Other Flash memory cards
Memory stick, CompactFlash, and
SD (secure digital) cards are the major oppnents in the market. Newer xD cards offer faster transfer rates as compared to older Flash standards such as Smart media or
MMCs (multimedia cards). But their speed has nomatch to SD cards. Therfore SD cards are much more popular in PDAs, digital audio players, or other digital
devices.
Extreme Digital cards are also available in smaller form factors like other flash standards. Being a proprietary format Olympus and Fujifilm similar to Sony Memory Stick, these cards offer no comparison to open CompactFlash and open SD card standards. A relatively low variety of xD card readers and accessories is available.
Though a wide range of capacities of xD cards is avaiable. But as the capacity increase speed decareses. So xD cards are comparable inlow capacities and mostly used in digital cameras. Moreover they are a bit expensive than other Flash standards.
