Appendix F: PC Cards

Appendix F: PC Cards

Laptop computers typically include PCMCIA slots for attaching peripherals. PCMCIA stands for Personal Computer Memory Card International Association, a nonprofit organization that has standardized the interface for adding memory cards to laptop computers. Although originally conceived for memory cards, PCMCIA devices became popular for a wide variety of add-ons for laptops. Today, laptop computers use many PCMCIA devices, such as modems, network cards, SCSI controllers, and sound cards. Using Linux on a laptop means having to use the PCMCIA devices, or PC Cards, as the popular press calls them nowadays. Thanks to the efforts of David Hinds, you can now use PCMCIA devices under Linux with his PCMCIA Card Services for Linux. This appendix briefly describes PC Cards that use the PCMCIA interface and the PCMCIA support package for Linux.


I refer to the actual cards as PC Cards because that's the proper name for the devices. PCMCIA refers to the industry organization that specifies the standard for PC Cards. However, I use the term PCMCIA Card in one context-when referring to PCMCIA Card Services for Linux (or Card Services, for short), the software that supports PC Cards under Linux.

PC Card Basics

PC Cards originated as static random access memory (SRAM) and flash RAM cards used to store data on small laptop computers. The credit-card-sized cards fit into a slot on the side of the laptop. The flash memory cards used electrically erasable programmable read-only memory (EEPROM) to provide laptop storage capability that might have been too small for other conventional storage media.

Vendors soon realized the convenience of the memory-card slot as a general-purpose expansion slot for laptop computers. The Personal Computer Memory Card International Association (PCMCIA) standardized various aspects of PC Cards, including the electrical interface, card dimensions, and card-slot sizes. This standardization has contributed to the proliferation of PC Cards in the laptop market.

By now, PCMCIA slots are a feature of almost all laptops, and the memory card is a small part of the overall PC Card market. Most laptops provide PCMCIA slots so that users can add hardware, such as fax/modems, sound cards, network cards, SCSI cards, and even hard disks.

Insider Insight 

To learn more about PCMCIA (the association) and PC Card specifications, point your favorite Web browser to For information about PCMCIA support in Linux, visit the Linux PCMCIA Information page at

PC Card Physical Specifications

PC Cards are divided into three different classifications, according to the thickness of the card. Following are the standard physical dimensions for each type of PC Card, in terms of width by length by thickness:

  • Type I PC Card-54 mm by 85.6 mm by 3.3 mm

  • Type II PC Card-54 mm by 85.6 mm by 5 mm

  • Type III PC Card-54 mm by 85.6 mm by 10.5 mm

All three types of PC Cards have the same length and width-the size of a standard credit card, except that credit card corners are rounded. The cards, however, are thicker than credit cards, and the card types are differentiated by thickness.

The term form factor is often used to refer to the dimensions of PC Cards.

All PC Cards use the same 68-pin connector. Because of this connector, a thinner card (Type I, for example) can be used in a thicker slot (Type II, for example). As you might guess, a thicker card cannot be used in a thinner slot, because you cannot physically insert a thick card into a thin slot.

Typical PC Card Applications

Each type of PC Card is used for a specific type of application. Following are the typical applications of PC Cards, by card type:

  • Type I PC Card-These thin cards are used for memory devices, such as static RAM (SRAM) and flash RAM.

  • Type II PC Card-These cards are used for input and output (I/O) devices, such as fax/modems, network adapters, and sound cards.

  • Type III PC Card-These cards are used for devices that need the added thickness, such as hard disks with rotating components (hard to believe, isn't it?).

A PC Card can have a maximum length of 135.6 mm (slightly longer than 5.25 inches), meaning the card can extend outside the host. Such extended cards are used for devices such as removable media, transceivers, and antennas.

PCMCIA Standards

All these specifications are described in the PCMCIA Standard, of which there have been three major releases:

  • PCMCIA Standard Release 1.0 (June 1990)-The initial standard defined the 68-pin connector and Type I and Type II PC Cards. This standard also defined the Card Information Structure (CIS) that has been the basis for interoperability of PC Cards. The first release of the PCMCIA Standard did not account for any I/O cards; only memory cards were considered.

  • PCMCIA Standard Release 2.0, 2.01, 2.1 (1991-94)-The second release of the standard defined an I/O interface for the 68-pin connector. Release 2.01 added the PC Card AT Attachment (ATA) specification and provided an initial version of the Card and Socket Services (CSS) Specification. Release 2.1 further enhanced the CSS Specification.

  • PC Card Standard (February 1995)-The current release of the standard has a new name: it is called the PC Card Standard, instead of the PCMCIA Standard. This release of the standard adds information to improve compatibility among different types of PC Cards and includes support for features such as 3.3-volt operation, DMA support, and 32-bit CardBus bus mastering.

PC Card Terminology

As all laptop vendors have adopted PC Card slots, the PC Card market has experienced explosive growth. Thanks to the PCMCIA Standards, the PC Card devices can be used in any PC Card slot. As you use PC Cards, you'll run into some special terms, including the following:

  • Card information structure (CIS)-This describes the characteristics and capabilities of a PC Card, so that the operating system or driver software can configure the card.

  • CardBus-This is an electrical specification that describes the use of 32-bit bus mastering technology and enables PC Cards to operate at up to 33 MHz.

  • Direct Memory Access (DMA)-This has the same meaning as in other peripherals; now PC Cards can use DMA technology.

  • Execute in Place (XIP)-This refers to the feature that enables operating-system and application software to run directly from the PC Card without having to be loaded into the system's RAM, which eliminates the need for too much system RAM.

  • Low-voltage operation-This refers to the ability of PC Cards to operate at 3.3 volts (as well as at 5 volts). The connector has a physical key to ensure that you do not inadvertently insert a 3.3-volt card into a 5-volt slot.

  • Multifunction capability-This enables a PC Card to support several functions. 3Com's 3C562, for example, is a 10Base-T Ethernet card and a 28,800-bps modem in a Type II form-factor PC Card.

  • Plug and Play-This enables you to insert or remove a PC Card while the system is turned on (this is known as hot-swapping). You can hot-swap PC Cards by making the power-connection pins the longest, so that the data lines disconnect before the power.

  • Power management-This refers to the capability of PC Cards to interface with the Advanced Power Management (APM) capabilities of laptops through the Card Services Specification.

  • Zoomed video (ZV)-This refers to a connection between a PC Card and the system's video controller that enables the card to write video data directly to the video controller.