Compact Flash
CompactFlash (CF) is a type of data storage device, used in portable electronic devices. It uses a variety of flash memory in a standard-sized enclosure. It was first specified and produced by SanDisk Corporation.
CF was the first such flash memory standard, built around Intel's NOR-based flash memory. NOR-based flash has lower density than newer NAND-based systems, and Compact Flash is therefore (in spite of its name) much larger than competing standards like MMC or Memory Stick.
Compact Flash defines a smaller physical interface that is electrically identical to the PCMCIA-ATA interface. That is, it appears to devices as if it were a hard drive of some defined size. The connector is about 42 mm wide, and the case comes in two standard sizes, CF I at 3.3 mm thick, and CF II at 5 mm thick. Both are otherwise identical.
They are non-volatile and solid state, thus more durable than disk drives, and consume around 5% of the power required by small disk drives. They operate at 3.3 volts and 5 volts, and can be swapped from system to system. CF cards are able to cope with extremely rapid changes in temperature. Industrial versions of CF cards can operate at a range of -45 to +85 °C.
Used in handheld devices (which won't take larger form-factor cards), digital cameras, and a wide variety of other uses, including desktop machines.
Microdrives
Originally released in 1999 by IBM in a 340 megabyte capacity, Microdrives are tiny hard drives that fit into the CF II format. Although these drives can fit into any CF II slot, they only work with Microdrive compatible devices. They also require more care than flash memory, as they are sensitive to physical shock and temperature changes. In December 2002 Hitachi bought IBM's disk drive business, including the Microdrive brand. Microdrives are available in capacities of up to 4 GB.
CF+ specification
When Compact Flash was first being standardized, even hard drives were rarely larger than 4 GB in size, and so the existing limitations of the ATA standard were considered acceptable. Since then hard drives have had to make many modifications to the ATA system to handle ever-growing media, and today even flash memory cards have been able to reach the limits.
For this reason a new CF standard, CF+ (or CF 2.0), has been drawn up. It includes two major changes, an increase in speed to 16 MB/s data-transfer, and capacities up to 137 GB.
As of 2004, Compact Flash cards are available in megabytes in powers of 2, from 8 MB to 8 GB.
Other devices in the format
The Compact Flash format is also used for a variety of Input/Output and interface devices. Since it is electrically identical to the PC Card, many PC cards have CF counterparts. Some examples include:
See also
