PCMCIA memory cards and storage cards are used to add memory (RAM, SRAM, Flash, etc.) and/or storage capacity (hard disks, CD-ROM, etc.) to computers. PCMCIA is an acronym for the Personal Computer Memory Card Association, the organization which develops and maintains standards for PCMCIA cards. Originally, these devices were known as PC cards because they were designed to add memory to portable computers. As PCMCIA standards and technologies evolved, however, these cards were added to many types of devices. Product specifications for PCMCIA memory cards include technology standard, card form factor, and memory type. Storage capacity and performance, power requirements, and other parameters are also important to consider.
There are several major technology standards for PCMCIA memory cards. PC Card Standard 95 is the original PCMCIA device standard. It has a 68-pin interface with 16 bits of address and data. CardBus technology runs at 33 MHz and is for cards with 32 bits of address and data. Miniature card technology products are about one-fourth the size of PC Card Standard 95. These PCMCIA memory cards use StrataFlash® (Numonyx B.V.) technology, a multilevel cellular architecture; and µBGA, a type of ball grid array. CompactFlash® (CompactFlash Association) is a very small, removable, mass storage PCMCIA device that weighs a half-ounce and is the size of a matchbook. Other unlisted technology standards for PCMCIA memory cards include SmartMedia and CardBay.
Memory type is important to consider when selecting PCMCIA memory cards. There are three major categories of memory: flash, DRAM and SRAM, and ROM. Flash memory cards use ATA flash, CompactFlash, linear flash, or StrataFlash. Dynamic RAM (DRAM) stores each bit of data in a separate capacitor. Static RAM (SRAM) is more expensive than DRAM, but faster and more reliable. Synchronous SRAM is synchronized with the system clock. Asynchronous SRAM is not. Read-only memory (ROM) retains its contents even when the computer is turned off. ROM types for PCMCIA memory cards include one-time programmable read-only memory (OTP-RPM), erasable programmable read-only memory (EPROM), and electrically erasable programmable read-only memory (EEPROM).
PCMCIA memory cards are categorized by form factor. Type I cards are 54 mm x 85.4 mm, and can be up to 3.3 mm thick. They are commonly used are used in RAM, ROM, and Flash RAM applications. Type II cards are 54 mm x 85.4 mm, and can be up to 5.5 mm thick. They are commonly used in I/O devices such as data/fax modems, and in LAN adapters and non-rotating mass storage devices. Type III cards are 54 mm x 85.4 mm, and can be up to 10.5 mm thick. They are commonly used as hard drives. Type IV cards have not yet been ratified by the PCMCIA consortium; however, their size is expected to be 54 mm x 85.4 mm with a thickness of 18 mm. They will be used in large capacity hard drives. Additional form factors for PCMCIA memory cards include SmartMedia Card, CompactFlash, Miniature Card, Solid State Floppy Disk (SSFDC), and MultiMediaCard (MMC).