What is a PCMCIA Card?

A Personal Computer Memory Card International Association (PCMCIA) card is a type of interface card for laptop computers. The PCMCIA defined and developed the PCMCIA card to compete with the Japan Electronic Industries Development Association (JEIDA) memory cards. These two standards merged in 1991, and the PCMCIA 2.0 standard is equivalent to the JEIDA 4.1 standard.

The development of a standard for laptop peripheral interface cards led to a variety of PCMCIA cards. The first PCMCIA card provided memory expansion, and these were soon followed by modems, network cards and hard drives that used the PCMCIA standard. Notebook computers in the 1990s used a PCMCIA card, which were largely replaced by the faster ExpressCard cards in 2003. Early digital cameras also used a PCMCIA card.

A PCMCIA card started being called a PC card with version 2.0. This reflected the fact that the acronym "PCMCIA" is long and often difficult to remember. Additionally, the scope of the PCMCIA standard has broadened beyond its original use as a memory card. The PCMCIA acquired the rights to the name "PC Card" from the International Business Machines (IBM) Corporation.

PC Card devices use an interface consisting of two identical rows of 68 pins. They measure about 3.4 inches (85.6 mm) by 2.1 inches (54 mm), which is about the size of a credit card. A PC card might use 3.3 volts or 5 volts, and some devices can run at both voltages. A 3.3-volt card has a key on the slot to prevent it from being inserted into a 5-volt slot.

A Card Information Structure (CIS) is stored on all PC Card devices, which describes how the data on the card is formatted and organized. The CIS contains specific information such as the manufacturer, model number, card type, power supply and power saving features. A damaged CIS is frequently the cause of an unrecognizable PC Card.

A device that uses PCMCIA 5.0 or later is specifically called a CardBus, which became the standard interface for laptops by 1997. A CardBus device uses a 33 MegaHertz PCI bus and supports bus mastering, meaning that a bus controller can communicate with other devices without going through the central processing unit (CPU).

A CardBus device is a 32-bit device, so it can't be plugged into a 16-bit slot. Most laptops have slots that accept both 32-bit and 16-bit devices as of 2010. A CardBus device has a gold band on top of the card to distinguish it from older devices.