 A 16 MiB Fujifilm xD Card |
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| Media type | memory card |
|---|---|
| Capacity | maximum 512 MiB (original) maximum 2 GiB (Type M/M+, Type H) |
| Developed by | Olympus, Fujifilm |
| Dimensions | 20 mm × 25 mm × 1.78 mm |
| Weight | 2.8 grams |
| Usage | digital cameras, voice recorders |
xD-Picture Card is a type of flash memory card, used mainly in digital cameras. xD originally stood for extreme Digital.[1] The cards were developed by Olympus and Fujifilm, and introduced into the market in July 2002. Toshiba Corporation and Samsung Electronics manufacture the cards for Olympus and Fujifilm. xD cards are now sold under other brands, including Kodak, SanDisk, PNY, and Lexar, but are not branded with the respective companies' logos, except for Kodak.
xD cards are used in Olympus and Fujifilm digital cameras and Olympus digital voice recorders; Fujifilm also made an MP3 player (xD-MP3) that used the cards. As of 2008[update], xD cards are available in capacities of 16 MiB up to 2 GiB.
As of June 2009[update], it appears that Olympus is beginning to move away from the xD card with the release of the E-P1 camera; it supports only SD memory cards.[2] Likewise, Fujifilm has also phased out support for xD in favor of SD and SDHC.[3]
Contents |
Type M/M+ and Type H cards
The original xD cards were available in 16 Mb to 512 Mb capacities. The Type M card, released in February 2005[4], uses multi-level cell (MLC) architecture to achieve a theoretical storage capacity of up to 8 Gb. As of August 2006[update], Type M cards are available in sizes from 256 MiB to 2 Gb. However, the Type M suffers slower read-write speeds than the original cards.
The Type H card, first released in November 2005[5], offers higher data rates than Type M cards (theoretically as much as 3 times faster). As of 2008, Type H cards were only available in 256 Mb, 512 Mb, 1 Gb, and 2 Gb capacities. Both Fuji and Olympus discontinued the production of Type H cards in 2008, citing high production costs[6].
The Type M+ card, first released in April 2008[7], offers data rates 1.5 times that of Type M cards. As of 2008, cards are available only in 1 and 2 Gb capacities.
Olympus says that its xD cards support special "picture effects" when used in some Olympus cameras, though these software features are not intrinsically hardware-dependent. Type H and M+ cards however, are required in newer models to capture video at high rate (640×480×30). Due to changes in the cards' storage architecture, newer Type M and H cards may suffer compatibility issues with some older cameras (especially video recording). Compatibility lists are available for Olympus: Olympus America’s and Fujifilm’s. The newer cards are also incompatible with some card readers.
Theoretical transfer speeds
Pictures may be transferred from a digital camera's xD card to a personal computer by plugging the camera into the PC (via a USB cable), or by removing the card from the camera and inserting it into a card reader. In both cases, the computer sees the card as a mass storage device containing image files, although software or firmware can alter this representation. Card readers may be integrated into the PC or attached via cable. Adapters are available to allow an xD picture card to be plugged into other readers (and in some cases cameras), including PC card, parallel port, CompactFlash and SmartMedia.
| Type | Write speed (MiB/s) |
Read speed (MiB/s) |
Capacities Available | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 16 MiB | 32 MiB | 64 MiB | 128 MiB | 256 MiB | 512 MiB | 1 GiB | 2 GiB | |||
| Standard | 1.3 | 5 | Yes | Yes | No | No | No | No | No | No |
| 3 | 5 | No | No | Yes | Yes | Yes | Yes | No | No | |
| M | 2.5 | 4 | No | No | No | No | Yes | Yes | Yes | Yes |
| H | 4 | 5 | No | No | No | No | Yes | Yes | Yes | Yes |
| M+ | 3.75 | 6 | No | No | No | No | No | No | Yes | Yes |
Comparison with rival formats
As of 2008, the xD format primarily competes with Secure Digital card (SD), CompactFlash (CF), and Sony's Memory Stick.
Advantages
- Does away with the hard-drive emulating Flash Translation Layer (FTL), which allows better designed flash file systems direct access to the hardware
- Is very similar to standard NAND chip, thus with proper modifications, its possible to use XD reader to read arbitrary NAND chips
Disadvantages
- xD cards have a small maximum capacity relative to other memory card formats. First-generation xD cards have a maximum capacity of only 512 MiB; while Type M expands the theoretical maximum capacity to 8 GB, but as of January 2009[update] there are no cards available with capacity greater than 2 GiB.
- xD cards have not kept up with the transfer rate, or speed, of other cards, notably Compact Flash and SD but also the later versions of the Memory Stick. The fastest xD card offers less than 10% of the speed of current (2009) Compact Flash cards.[citation needed]
- Although physically smaller than Secure Digital and Memory Stick cards, xD cards are larger than these competitors' reduced-size variants (microSD, and Memory Stick Micro).
- xD cards are generally more expensive than other memory card types. As of September 2009[update], 2 GiB xD cards' retail prices are approximately three times those of same-capacity SD cards.
- xD cards are less widely supported by camera, card reader, and accessory manufacturers than other formats.[8]
- Because the xD is directly derived from the Smart Media card and is electrically identical (though not necessarily format identical) to that card, the xD card contains no wear levelling controller. Thus the xD card may have a shorter life than comparable cards with FTL wear levelers if the file system used does not take into account wear leveling
- The xD card format is proprietary to Fujifilm and Olympus, just as the Memory Stick format is to Sony. This means that no public documentation or implementation is available (see below for reverse-engineering results). By comparison, the CompactFlash format is described by completely open and free specifications, and a partial specification for the SD format is freely available.
Detailed specifications
The detailed specification for xD cards is tightly controlled by Olympus and Fujifilm, which charge licensing fees and royalties and require non-disclosure agreements in exchange for the technical information required to produce xD-compatible devices.[9]
The memory format used by xD cards is not well-documented. It is difficult to study it directly, since most camera devices and most USB card readers do not provide direct access to the flash memory. Since the cards are controller-less, cameras and card readers must perform wear leveling and error detection themselves, and they normally hide the portion of the memory which stores this information (among other things) from higher-level access.[10]
However, a few models of xD card readers based on the Alauda chip do allow direct access (bypassing the above mechanisms) to an xD card's flash memory; these readers have been reverse-engineered and Linux drivers have been produced by the Alauda Project, which has also documented the on-chip data structures of the xD card. According to this information, the xD card headers are similar to those used by SmartMedia, and include information on the manufacturer of the chip.
Raw hardware
At the raw hardware level, an xD card is simply an ordinary NAND flash integrated circuit in an unusual package. Comparing the pinout of an xD card[11] to the pinout of a NAND flash chip in a standard TSOP package,[11] one finds a nearly one-to-one correspondence between the active pins of the two devices. xD cards share this characteristic with the older SmartMedia cards, which are also basically raw NAND flash chips, albeit in a larger package.
xD cards and SmartMedia cards can be used by hobbyists as a convenient source of NAND flash memory chips for custom projects. For example, the Mattel Juice Box PMP can be booted into Linux using a modified cartridge containing an xD card with the boot image written to it. Additionally, SmartMedia and xD card readers can be used to read the data off of NAND flash chips in electronic devices, by soldering leads between the chip and the card reader.[12]
Panoramic mode
Olympus-branded xD cards are the only ones that support Olympus cameras' panoramic function. Although they store data identically to other manufacturers' cards, Olympus intentionally disables this feature in the hopes that buyers will purchase their cards (a form of vendor lock-in).
However, it appears that the card manufacturer information is simply stored in the flash memory, in the Card Information Structure (described in the Alauda Project's documentation, see above). Thus, it is possible to alter another brand of xD card to present itself as Olympus xD card by accessing the raw flash memory.[13]
Market acceptance
Because of its higher cost and limited usage in products other than digital cameras, xD has been losing ground to SD, which is broadly used by PDAs, digital audio players, and most other digital camera manufacturers.
It is perhaps surprising that xD cards cost more than SD cards, since SD cards must contain a controller circuit in addition to the NAND flash memory. However, SD cards are produced in much greater numbers and by more manufacturers, so economies of scale and increased competition help explain the significant price disparity.
While many older Olympus and Fujifilm digital cameras use xD cards exclusively, many can access other memory card formats. In particular, the Olympus DSLRs, Fujifilm S7000, and Fujifilm S9500 can use CompactFlash in addition to xD. Newest Fujifilm FinePix cameras, including A, Z, S, and F series cameras, no longer use xD cards and only function with SD Cards. Some can accept both SD, SDHC, and XD cards. In March 2008, Olympus introduced an adapter (part number MASD-1) allowing its latest cameras to accept microSD cards in the xD slot. This adapter works only with recent models that were designed for it because the MASD-1 adapter is purely mechanical containing no electronic components, and thus relies on support for the SD card protocol within the cameras themselves, though this fact is not advertised by Olympus.[14]
It appears[original research?] that Olympus is beginning to move away from the xD card with the release of the E-P series cameras, the E-P1 memory specifictions state that the only format supported is SD memory cards.[2]
See also
References
- ^ 2002 press release, Fujifilm: "The name 'xD-Picture Card' was inspired by 'eXtreme Digital', …"
- ^ a b http://www.olympusamerica.com/cpg_section/product.asp?product=1461&page=specs
- ^ http://www.fujifilm.com/products/digital_cameras/accessories/card/
- ^ Olympus 1 Gb xD, Steve’s Digicams.
- ^ Olympus Type H xD, Steve’s Digicams.
- ^ http://www.dpreview.com/news/0801/08012301olympusxd.asp
- ^ Olympus Type M+, Olympus.
- ^ As of November 2007[update], SD cards (and variants) are supported by most or all consumer-level digital cameras from many major manufacturers. CompactFlash is the de facto standard for professional and prosumer cameras, accepted by virtually all digital SLR cameras, including those made by Olympus and Fujifilm. SD cards are also supported by many brands of MP3 players, PDAs, game consoles, and mobile phones.
- ^ How to obtain xD-Picture Card License
- ^ this page, which explains how to use an xD card as a source of raw flash memory chips for the Mattel Juice Box; the answer to question #3 at the bottom explains why most xD card readers cannot be used for raw access to the flash memory.
- ^ a b An xD card pinout from pinouts.ru. There is a pinout for a standard NAND flash chip on page 8 of Toshiba's NAND Design Guide.
- ^ xD NAND Flash Reader, Read Embedded Flash Chips, uchobby.com.*
- ^ One way to do this is by using a hacked device driver for a USB card reader, as described by Robert Haus.
- ^ "Forum posting: microSD to xD adapter works!". DPReview.com. 2008-03-23. http://forums.dpreview.com/forums/read.asp?forum=1008&message=27284154. Retrieved 2008-03-23.
External links
- Licensors' Official Site (Olympus and Fujifilm)
- XD-Picture Card Connector Pinout
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