What is xD?
xD is the abbreviated form for Extreme Digital. xD is mainly used in digital cameras to store digital pictures. It has a storage capacity from 16 Mega Bytes to 2 Giga Bites. The card was introduced in 2002 by Olympus and Fujifilm.
There are three types of xD cards available in the market. Type M Card, Type M+ Card, Type H card. Type M Card was released in 2005 February. Type M card uses multi-level cell architecture. It has a storage capacity up to 2 Giga Bytes and it can store two thousand pictures with one Mega Byte size each. In theory it has a storage capacity of 8GB, but it cannot be accomplished due to some limitation of its architecture. In future we can expect 8 Giga Byte xD cards from Fujifilm or Olympus. Read-Write speed of M-Card is very slow compared to other cards. Type H Card was released in 2005 November. It transfers information at an unmatchable rate. Type M+ card was released in 2008 April and it have higher read-write rate than that of M-Cards.
Through USB or IEEE 1394 cable you can connect digital camera’s xD card to your laptop or PC. You can insert the card into laptop’s card reader also. xD can directly access the NAND gates and it is better designed than any of it’s counter parts. It is very similar to standard NAND chip. Pin out of xD card and NAND chip are same. xD has less storage capacity compared to other memory cards available in the market now. On the basis of size xD card is much bigger. The cost of the card is also very high. xD cards are obsolete now because of it low transfer rate and high cost. Now SD cards are playing the major role in compact card market. Olympus and Fujifilm is tightly controlling the detailed specification for xD cards. They charge licensing fees and royalties.