From Academic Kids

The PCMCIA is the Personal Computer Memory Card International Association, an industry trade association that creates standards for notebook computer peripheral devices.

The best known such devices are known as PC Cards (formerly PCMCIA cards). A later revision of the PC Card is known as CardBus. The PCMCIA is also developing a new notebook peripheral specification called Newcard or ExpressCard. The initialism "PCMCIA" was jokingly expanded as "People Can't Memorize Computer Industry Acronyms".

The first PC cards (PCMICIA) 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 on this. The ports role as I/O for various devices has largely superceded its role as a Memory Card, but this role did spawn a generation of flash memory cards that set out to improve on the size and features of ATA Type I cards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 SSFDC(Smartmedia)).

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

PC Card

A PC Card is about the size of a credit card. There are three different sizes, varying in thickness: Type I is 3.3mm thick, Type II is 5.0mm thick and Type III is 10.5mm thick. All are 85.6mm long and 54.0mm 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. Fortunately, most Type III cards were normally external hard disks that have since been replaced with USB and FireWire solutions, along with flash memory options. Memory cards such as ATA Type I flash memory cards continue to be available for the PC Card Type I.

As per the original name, 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 satellite TV systems.


The original PCMCIA bus is 16-bit, similar to ISA. CardBus is effectively a 32-bit, 33MHz 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 slots are compatible with both the CardBus and the original 16-bit cards.

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.

ExpressCard (Newcard)

The PCMCIA has developed a replacement for the present CardBus standard, called ExpressCard, which is claimed to be faster and less complex than CardBus. The name Newcard was at one stage potentially to be used for this. The host device supports both PCI Express and USB 2.0 connectivity through the ExpressCard slot, and each card uses whichever the designer feels most appropriate to the task. The cards are hot-pluggable.

ExpressCard supports two form factors, ExpressCard/34 (34mm wide) and ExpressCard/54 (54mm wide, in an L-shape - the connector is the same width (34mm) on both). Standard cards are 75mm long (10.6 mm shorter than CardBus) and 5mm thick, but may be thicker on sections that extend outside the standard form factor - for antennas, sockets, etc.

Dell Computer said it would start shipping machines using ExpressCard in the second half of 2004. [1] (,aid,114876,tk,dn022304X,00.asp) And Hewlett-Packard actually did it. [2] (,1759,1706542,00.asp) A large number of ExpressCard devices were presented at the CeBit trade show in Germany in March 2005. [3] (

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