A CompactFlash (CF) card is a popular memory card developed by SanDisk in 1994 that uses flash memory technology to store data on a very small card. It has no moving mechanical parts and does not need a battery to retain data. CF cards allow users to add data to a wide variety of computing devices.
Based on the Parallel Advanced Technology Attachment (PATA) interface, CF cards measure 42.8 x 36.4 mm (about the size of a matchbook) and are available with storage capacities ranging up to 512 gigabytes (GB). There are two types of CF cards, in varying thicknesses, to accommodate different capacities: Type I CF cards are 3.3 mm thick vs. 5.0 mm for Type II cards.
CompactFlash cards support 3.3V and 5V operation, and can switch between the two. This varies from other small form factor flash memory, which can only operate at one voltage.
Because flash is nonvolatile memory, stored data is retained when a device's power source is turned off or lost. CF cards feature solid-state construction, which makes them much more rugged than most traditional storage devices. The operating shock rating (basically, what height can you drop them from and have them still work) for CF cards is 2,000 G compared to a 100 G to 200 G rating for the mechanical drive of a typical portable computing device. This translates to a drop to the floor from 10 feet vs. a single foot for the mechanical disk drive.
CompactFlash is a popular card choice for use with digital single-lens reflex (DSLR) cameras. A high-end version, Ultra CompactFlash, is optimized for more demanding photography, such as a quickly shot succession of high-resolution pictures or pictures of a moving subject. Ultra CF provides a transfer rate twice that of SanDisk's standard memory cards, allowing data to be quickly saved and the camera to be ready to capture another image.
CFast, or CompactFast, combines the CompactFlash card form factor with the Serial ATA (SATA) interface.
CompactFlash card compliance
CF cards are self-tested for interoperability by member manufacturers of the CompactFlash Association, which was established in 1995. Cards completing this testing are labeled as follows:
- CF 4.1a: Products are widely available at speeds up to 90 megabytes per second (MBps) sequential access speed.
- CF 5.0: Products have more efficient commands and support TRIM operations providing consistent speed.
- CF 6.0: Implements Ultra Direct Mode Access 7 (UDMA 7), which provides bus speeds up to 167 MBps, and supports the Sanitize command.
Additional flash memory card formats
To save and transfer files, images and songs among devices that are ever decreasing in physical size, newer flash memory card formats have been introduced. For example, Secure Digital (SD) memory cards -- which are regulated by the SD Association, an industry organization similar to the CompactFlash Association -- come in a variety of styles and capacity. SD cards are 32 x 24 x 2.1 mm in size. They are easy to spot due to their cut-corner profile.
MiniSD and microSD memory cards have been designed for use in mobile phone technology. MiniSD cards are 21.5 x 20 x 1.4 mm in size, while microSD cards are 15 x 11 x 1 mm in size.
The main difference between SD cards and CF cards is that SD cards do not contain a microcontroller.
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