Source:
http://www.compactflash.org/faqs/faq.htm
What is CompactFlash?, CF Type I, CF Type II and CF I/O?
CompactFlash? is a small, removable mass storage device. First introduced in 1994, CompactFlash cards weigh a half ounce and are the size of a matchbook. They provide complete PCMCIA-ATA functionality and compatibility.
At 43mm (1.7") x 36mm (1.4") x 3.3mm (0.13"), the CF Type I card's thickness is less than one-half of a current PCMCIA Type II card. It is actually one-fourth the volume of a PCMCIA card. Compared to a 68-pin PCMCIA card, a CF card has 50 pins but still conforms to ATA specs. It can be easily slipped into a passive 68-pin PCMCIA Type II to CF Type I adapter that fully meets PCMCIA electrical and mechanical interface specifications.
At 43mm (1.7") x 36mm (1.4") x 5mm (0.19"), the CF Type II card's thickness is equal to a current PCMCIA Type II card. It is actually less than one-half the volume of a PCMCIA card. Compared to a 68-pin PCMCIA card, a CF card has 50 pins but still conforms to ATA specs. It can be easily slipped into a passive 68-pin PCMCIA Type II to CF Type II adapter that fully meets PCMCIA electrical and mechanical interface specifications.
The only difference between CF Type I and CF Type II cards is the card thickness. CF Type I is 3.3 mm thick and CF Type II cards are 5mm thick. A CF Type I card will operate in a CF Type I or CF Type II slot. A CF Type II card will only fit in a CF Type II slot. The electrical interfaces are identical. CompactFlash is available in both CF Type I and CF Type II cards, though predominantly in CF Type I cards. The Microdrive is a CF Type II card. Most CF I/O cards are CF Type I, but there are some CF Type II I/O cards.
CompactFlash cards are designed with flash technology, a nonvolatile storage solution that does not require a battery to retain data indefinitely.
CompactFlash storage products are solid state, meaning they contain no moving parts, and provide users with much greater protection of their data than conventional magnetic disk drives. They are five to ten times more rugged and reliable than disk drives including those found in PC Card Type III products. CF cards consume only five percent of the power required by small disk drives.
CompactFlash cards support both 3.3V and 5V operation and can be interchanged between 3.3V and 5V systems. This means that any CF card can operate at either voltage. Other small form factor flash cards may be available to operate at 3.3V or 5V, but any single card can operate at only one of the voltages.
CF data storage cards are also available using magnetic disk (Microdrive).
CF I/O cards include modems, Ethernet, serial, Bluetooth wireless, digital phone cards, USB, laser scanners, etc.
The connector used with CF and CompactFlash is similar to the PCMCIA Card connector, but with 50 pins. Years of field experience in portable devices have proven the reliability and durability of this connector in applications where frequent insertions and ejections of the card are required. Other small form factor flash cards use connector technology that is not reliable or durable in these applications .
CompactFlash provides the lowest cost flash storage solution for capacities of 16MB and above. With the built-in controller, a wide variety of low cost flash technologies can be used. The built-in controller lowers costs further by reducing costs in the host device and allowing defective flash chip cells to be mapped out, thus increasing flash chip yields. Microdrives provide the lowest cost data storage solution for capacities of 340MB and above.
When compatibility, interoperability, reliability, cost, and performance count, CF and CompactFlash cards are the ATA-compatible solution that delivers.
