CompactFlash

CompactFlash (or CF) cards are small expansion cards aimed primarily at the mobile technology markets. The CompactFlash standard was first introduced by the CompactFlash Association in 1994.

A typical CompactFlash card will weigh in at half an ounce and are (typically) the size of a matchbook. They provide complete PCMCIA-ATA functionality and compatibility.

There are two subset types and form-factors of CF cards: They are

• CF Type I
  43mm (1.7") x 36mm (1.4") x 3.3mm (0.13").
  
  
• CF Type II
  43mm (1.7") x 36mm (1.4") x 5.5mm (0.19").
  
  

..the only real difference between CF Type I and Type II is the thickness.

Although mostly used for non-volitile data storage, the CF I/O Spec (being similar to the PCMCIA I/O Spec (Version 2.1)) allows the CF form factor (via CF+ in some cases) to be employed for other technologies such as modem, ethernet, ATA Hard drives and data collection devices. Additonally, the CF standard calls for cards that can operate in both 3.3v and 5v systems.

Compactflash (memory) cards have many intended and unintended uses. They are marketed as "film" for digital cameras, where they see wide use. Some portable MP3 players can read CF cards, which is a boon for users as solid state alternatives (generally fixed, MMC, or Flashmedia) have not reached the commodity price point of CF.

Because CF (memory) cards provide ATA functionality it is trivial to press them into service solid state disk ("SSD") drives. Compared with "real" SSD drives (often used in the military; Quantum makes one) CF cards have a shorter design life than standard DRAM, with a nominal expectation of 100,000 write cycles (reads have negligible impact on flash memory). This is offset by the availability of CF media at a fraction of the cost.

Common Uses

• digital cameras
• mp3 players
• portable and PDA computers

Creative Uses

• server farms, sans mechanical disks
• standalone diskless workstations (i.e. no BOOTP server)
• "cheap", low-power, solid-state RAID array (ATA-firewire bridge chips work well)
• PGP key storage
• internationally portable DeCSS mirror ;-)

The Compact Flash card is a smaller version of the Type I PCMCIA card, the original version of which is almost obsolete. As one could infer from the name, it uses flash memory. Compact Flash is currently the most popular form of removable memory for digital cameras. It's also widely used in PDA's.

The size specificatons are as follows:

Length 1.433 in (36.4 mm) Width 1.685 in (42.8 mm) Height 0.130 in (3.30 mm) Weight 0.36 oz (10.2 g)

Compact Flash cards typically have more space than their memory stick contemporaries and definitely more than Smart Media cards. SmartMedia cards are also wafer thin and easy to break, whereas you can toss a Compact Flash card out of a two-story window onto pavement, and it will usually continue to function. I've left one in my pocket more than once on laundry day, and it came out of the washer/dryer still functioning.

Currently, the leading developers of CF cards are SanDisk and Lexar Media. SanDisk focuses on producing cards for storage, whereas Lexar Media cards are optimized for digital cameras, with a binary writing style which works faster and allows for less write time between pictures.

Lexar Media also recently introduced and licensed USB enabled compact flash cards, which come loaded with all the USB interface technology in the card. They are packaged with a cord to connect the card to any USB slot.



specification info found at: http://www.lexarmedia.com/products/usb_cf_main.html

The above writeup fails to mention the standard sizes of Compact Flash cards. These are

• 8 MB
• 16 MB
• 32 MB
• 64 MB
• 128 MB
• 160 MB
• 192 MB
• 256 MB
• 512 MB
• 1.0 GB

There is also a huge price difference between No-Name cards and brand cards, and while there may be minute differences in speed, I have not yet seen one of my No Namers break down despite some of the punishment I have put them through. And the price difference can be enormous, up to 100 %, especially in the larger, and therefore newer sizes.

At this point, the best choice of size when comparing the MB per monetary unit, is the 256 MB CF Card, but this may change in a years time. One 256 MB card is slightly cheaper than two 128 MB card, and two 256 MB card are still a better deal than one 512 MB card, although the prices of these are still falling. 1 GB cards, when available (they are still very rare, as these cards are very new items, I have only seen them twice while wandering my favorite Hi-tech-wonderland, Akihabara), are still priced prohibitively, and unless you really need one big card, you are better off with, say, 8 256 MB cards.

The development of CF-Cards still continues, and while other systems such as the SD Card and Memorystick are now being pushed because of better digital rights management (CF has no such thing), they still hold the biggest market share. Additionally, CF-cards have always been the largest portable memory cards on the market. I have yet to see Memorysticks or SD-Cards of 512 MB or larger. I am curious, how much flash memory they can go on fitting into this small space.