PC card From Wikipedia, the free encyclopedia

Portable Computer Cards (PC cards) are interchangeable peripherals designed to be inserted into laptop computers in order to enable extra hardware functions. Such cards include (but are not limited to) flash memory, modems, network interface cards, and SCSI disk controllers.

They were first called PCMCIA cards as the original standards were set by the Personal Computer Memory Card International Association. This awkward initialism was jokingly expanded as "People Can't Memorize Computer Industry Acronyms" or "Personal Computer Manufacturers Can't Invent Acronyms". A later revision of the PC card is known as CardBus. The PCMCIA is also developing a new notebook peripheral specification called ExpressCard.

The first PC cards (PCMCIA, with the more logical IBM meaning: Peripheral Component Microchannel Interconnect Architecture) were Type I, and supported actual Memory Cards (e.g. ATA Type I Flash Memory Cards), such as DRAM or flash memories. Type II cards added I/O support in addition to memory applications, and type III expanded functionality. The interface's role as I/O for various devices has largely superseded its role as a Memory Card, but this role did spawn a generation of flash memory cards that set out to improve on the size and features of ATA Type I cards (CompactFlash, MiniCard and SmartMedia).

Type II and III PC Cards. The Type III is twice the thickness of the Type II.
Type II and III PC Cards. The Type III is twice the thickness of the Type II.

PCMCIA cards were designed by US-industry to compete against the JEIDA cards that the Japanese portable computer industry had established as a standard for memory cards. Later, the two standards merged, and became JEIDA 4.1 or PCMCIA 2.0 in 1991.


Pre-unification PCMCIA cards (version 1.x spec) were only Type-1 cards.

PC card

PC cards are PCMCIA 2.0 or later (JEIDA 4.1 or later) 16-bit PCMCIA cards and were introduced in 1993. A PC card is about the size of a credit card. There are three different sizes, varying in thickness: Type I is 3.3 mm thick, Type II is 5.0 mm thick and Type III is 10.5 mm thick. All are 85.6 mm long and 54.0 mm wide. Most notebooks used to come with two Type II slots or one Type III. With the removal of legacy ports, most notebooks now only come with one Type II card slot. This is often acceptable since most Type III cards were normally external hard disks that have since been replaced with USB, FireWire and now Serial ATA solutions, along with flash memory options. Toshiba introduced a 16 mm Type IV card that was never sanctioned by PCMCIA. Memory cards such as ATA Type I flash memory cards continue to be available for the PC Card Type I.

As the original name suggests, the first PC cards were for memory expansion. However, the existence of a usable general standard for notebook peripherals led to all manner of devices being made available in this form. Typical devices include network cards, modems and hard disks.

The electrical specification for the PC card is also used for CompactFlash, so a PC Card CompactFlash adapter need only be a socket adapter.

The form factor is also used by the Common Interface form of Conditional Access Modules for DVB broadcasts.


CardBus are PCMCIA 2.1 or later (JEIDA 4.2 or later) 32-bit PCMCIA cards and were introduced in 1995. The original PC Card bus was 16-bit, similar to ISA. CardBus is effectively a 32-bit, 33 MHz PCI bus, in the same physical form as the earlier cards. The notch on the left hand front of the card is slightly shallower on a CardBus card so a 32-bit card cannot be plugged into a slot that can only accept 16-bit cards. Most new slots are compatible with both CardBus and the original 16-bit PC Card devices.

CardBus includes the bus mastering ability, which allows a controller on the bus to talk to other devices or memory without going through the CPU. Many chipsets are available for both PCI and CardBus cards, such as those that support Wi-Fi.

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