ARCHIVED: What is PCMCIA, and what is a PC card?

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PCMCIA is an acronym for Personal Computer Memory Card International Association; the acronym is pronounced as separate letters. PCMCIA is a non-profit trade association and standards body consisting of some 500 companies. PCMCIA has developed a standard for small, credit card-sized devices, called PC cards, that are often used in notebook computers. (Adapters are available that allow PC cards to be used in desktop computer systems.) You can visit the PCMCIA web site at:

  http://www.pcmcia.org

In the past, the cards were known as PCMCIA cards, but they are now referred to as PC cards, PC card hosts, and PC card software. PCMCIA refers to the association and standards body.

A PC card slot is an expansion slot often found in notebook computers that allows for the easy and quick addition of a host of different devices. Originally designed for adding memory to portable computer systems, the PC card standard has been updated several times since its original creation.

PC cards are Plug and Play devices that are often hot-swappable (i.e., cards may be removed and inserted with the computer power turned on, without rebooting) under Mac OS and Windows 95 and beyond. (Windows NT, however, has more limited support for PC cards, and you cannot change cards on the fly.) Many systems will give a familiar beep sound from the computer's speaker when you remove or insert a card.

Differences between PC cards

There are three different types of PC cards. All three have the same rectangular size (85.6 by 54 millimeters), but different thicknesses.

  • Type I cards can be up to 3.3mm thick, and are used primarily for adding additional ROM or RAM to a computer.
  • Type II cards (the most common) can be up to 5.5mm thick. These cards are often used for modem, fax, SCSI, and LAN cards.
  • Type III cards can be up to 10.5mm thick, sufficiently large for portable disk drives.

Differences between PC card slots

As with the physical PC cards, PC slots also come in three sizes:

  • A type I slot can hold one type I card
  • A type II slot can hold one type II card, or two type I cards
  • A type III slot can hold one type III card, or a type I and type II card.

Most notebook computer systems come with two PC card slots that allow for the use of two type I or type II PC cards and one type III PC card. The PC card slots are stacked with one above the other. Usually, type III PC cards fit only in the bottom slot.

Common PC card devices

Following is a list of common PC card devices:

  • CD-ROM interface
  • Cellular phone interface
  • Security tokens
  • Docking station interface
  • 10Mbps Ethernet LAN adapters
  • 100Mbps Ethernet adapters
  • GPS (Global Positioning System) cards
  • Hard drives
  • Infrared wireless LAN adapters
  • ISDN cards
  • Joystick interface cards
  • Memory cards
  • Modem and Ethernet combination cards
  • Parallel port interface
  • SCSI adapters
  • Serial port interface
  • Sound cards, input and output
  • Video capture/frame grabber cards
  • Video teleconferencing cards

Cardbus

Many laptop manufacturers now advertise their PC card slots as cardbus compatible, or they simply identify the slots as cardbus slots. Cardbus is an extension of the latest PCMCIA standard, which expands the bus bandwidth and throughput to 32 bits at 33MHz. In contrast, the older PC card standard was 16 bits at 8MHz. Cardbus is analogous to the PCI slots in desktops, while the older PC card standard is analogous to ISA. The newer cardbus slot can accommodate an older 16-bit PC card, but an older PC card slot cannot accept newer cardbus cards. To tell if your PC card is cardbus, look on the interface end of the card. Cardbus devices will have a notched metal plate on that end.

While not technically accurate, some vendors and technicians refer to the older style 16-bit PC card as PCMCIA in order to contrast it with 32-bit cardbus cards, which makes them sound like competing standards. However, cardbus is an extension to the PCMCIA standard, not a replacement.

For additional information, see:

  http://www.accurite.com/PCMCIAprimer.html

ExpressCard

The latest extension of the PCMCIA standard is called ExpressCard. This standard is being built on the latest USB 2.0 and PCI Express buses. The aim is to increase speed and reduce size, cost, and complexity. One of the ways it does this is to eliminate the PCMCIA Host Controller in favor of using the USB or PCI Express controller directly.

For additional information, see:

  http://www.expresscard.org/web/site/

This is document ahtn in the Knowledge Base.
Last modified on 2018-01-18 12:45:04.

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