What is PCMCIA and how does it work? (Personal Computer Memory Card International Association) (Compute's Getting Started with PCMCIA)
by Richard O. Mann

It hasn't been long since coat-pocket sized computers were the exclusive province of science fiction. Now science fiction writers--along with the rest of us--actually have computers as small as we could want. The challenge is not how to shrink them further but how to bring the power and expandability of desktop computers to the smallest PCs.

Obviously, there's noway to open up a palmtop computer and insert an extra memory board or modem, so a new way to provide these needed functions had to be developed. Enter the PCMCIA, or Personal Computer Memory Card International Association, a group that sets industry-wide standards for the tiny credit-card sized expansion devices that solve this problem. The association named the devices PC Cards, but you'll often hear them referred to as PCMCIA cards and slots.

The association was formed in 1989 as many manufacturers were preparing to create their own versions of memory cards for the new generation of portable computers. About 25 manufacturers met and agreed to work together to develop a standard that would allow the industry to create cards compatible with all computers.

The early organizers didn't realize the potential of what they were doing. "If I'd had any idea how this group would grow, I might have chosen a name that's easier to pronounce," says PCMCIA Chairman John Reimer, acknowledging the tongue-twisting nature of the group's name.

In four years, the association has grown to 350 member companies, with most of the major forces in the industry, including IBM, Toshiba, AT&T, Intel, Hewlett-Packard, and NCR. It has issued two standards and is close to issuing the third--see the accompanying article, "Three Types of PC Cards."

The PCMCIA standards specify both the hardware and software necessary to make PC Cards from any manufacturer compatible with any computer with a standard slot. The standard should enable system and card manufacturers to build products that can be operated by end users who lack any knowledge of the underlying technology.

By designing the PCMCIA standards, the association is creating a new standard bus for small computers. By complying with the standards, virtually any kind of device that can be attached to a desktop computer's ISA or other standard bus can be hooked into the tiniest pocket computer if the device's circuitry and components can be miniaturized sufficiently to fit on a PC Card.

Thus we see the whole gamut of enhancements coming to PC Cards, including various types of memory, fax modems, network adapter cards, hard disks, and other special-purpose devices.

Until now, laptop and notebook computer users found it either too difficult or too expensive to attach these functions to their computers. Modems were either specially made for each individual computer model or were external to the computer, requiring you to carry extra hardware. Network adapters would often hang off the parallel port or were in docking stations, which aren't portable at all.

The new generation of notebooks with PCMCIA slots is just beginning to appear. As PCMCIA slot-equipped notebooks flood the market, sales of PC Card devices will skyrocket. It's beginning to happen. As sales volumes pick up over the next few years,the prices of PC Card devices should fall, overcoming the last barrier to wide use of PC Cards.

By the way, PC Cards aren't limited to IBM-compatible PCs. They're used in other palmtop computers, such as the Psion Series 3, and will be used in Apple's Personal Digital Assistant (PDA), known as the Newton. Most pen computers will use them, as will any number of other special-purpose devices. They also should show up in non-computer consumer electronic devices such as electronic book players and digital cameras.

How Do PCMCIA Slots Work?

Each PC Card contains a basic record in a standard location, called the CIS, or Card Information Structure. The CIS describes the card's memory type, size, speed, and other characteristics in such a way that any host computer can read and respond to this information.

Two key elements of the PCMCIA software architecture are Socket Services and Card Services. Socket Services is a software interface running at the BIOS level that manages the host computer's use of the sockets in the PCMCIA slots. It identifies how many sockets are in the computer system and monitors for insertion or removal of PC Cards from the sockets. Cards can be inserted or removed without damage while the power is on (this is called hot swapping).

Card Services is a higher-level software-management interface that automatically allocates system resources, such as memory and interrupts, once it's notified by Socket Services that a PC Card is present. It also reallocates resources when notified that a card has been removed. Hardware drivers interact with Card Services to access the card in the slot.

Intel sponsors its own standard version of Card Services designed for the specific needs of Intel-based processors. The Exchange Card Architecture, or ExCA standard, was created before Card Services. Card Services was based on ExCA, but isn't Intel-specific.

With these services in place--as they are on any computer with a PCMCIA standard slot--you have complete freedom to pop cards in and out of your computer as your work demands. You don't have to worry about memory blocks, port assignments, or interrupt assignments; the PCMCIA interface software handles all of that automatically.

Since these Services and Release 2 of the standards are still new, the first machines and cards built to the standard are just appearing. There are still some glitches to work through before you can count on true interchangeability in every case. (The glitches now merely require the use of special device drivers at times. Eventually, these won't be necessary.) See the accompanying article, "Is PCMCIA a True Standard?" for more insight into this process. The industry is extremely confident that these problems will be worked out quickly.

A Bright Future

It's easy to get excited about the promise of PCMCIA's PC Card standards and what they can mean to the small-computer user. In fact, many believe that the success of the PCMCIA standard will fuel the expansion of the portable computer market beyond its already heady growth rate.

The Gartner Group predicts that by 1997, some 40 million computers, or about 60 percent of all worldwide desktop, notebook, and hand-held computers will have at least one PCMCIA slot.

Lampesis Research estimates that laptop, notebook, and pen computers presently comprise 22 percent of the computers sold in the United States. Three years from now, Lampesis estimates, over half the systems sold will be portable. And there's every likelihood that most, if not all, of those systems will have PCMCIA slots.

Analysts project that non-traditional computers used by an entirely new class of people will experience tremendous market growth. Pen-based computers, palmtop units, PDAs, and other mobile devices can allow workers to use their machines while standing and walking. Doctors and nurses making their rounds, insurance claims adjusters working at the site of an accident, sales people on the road meeting clients, inventory control clerks in warehouses, an truck drivers are all beginning to use these highly portable computerized tools in their work. These computers, too, are natural site for PCMCIA slots.

In any case, it seem clear that the PCMCIA standard PC Cards will play a big role in the future of computing. The standards are in place, the Card devices are ready to ship, and new computers are being built with PCMCIA slots. Even if you're not ready to participate in the boom yourself, it will be fascinating to watch this new technology burst into the computing world.