PCMCIA

All these bus standards presuppose one thing: that they will be used in a desktop box that has room and power available for expansion. But this underlying assumption runs directly contrary to one of the strongest currents in the PC mainstream-machine miniaturization that has led to notebook, sub-notebook, and palmtop computers. After all, an individual expansion board for one of these desktop standards likely stretches out longer than the largest dimension of most notebook machines. And a single board might draw more power than an entire notebook computer.

The world of movable computers has its own demands for expansion that were becoming apparent in 1987, by which time memory manufacturers were packing expansion RAM for notebook computers in slide-in credit card-size boards. In fact, memory cards of charge card dimension can trace their heritage back to the ROM cards used to store laser printer fonts as early as 1984.

Although such memory cards were becoming popular in 1987, no single standard existed. The industry leader at that time was Mitsubishi, whose memory cards used a proprietary 60-pin package. Fujitsu Microelectronics had a similar, competing line of memory cards and smart cards (Fujitsu's term for any small card with integrated circuits on it), but these were based on a 68-pin connector design.

John Reimer, upon being appointed marketing manager for microcomputer products at Fujitsu in 1987, quickly determined that he had inherited what amounted to a product looking for a purpose. It seemed to Reimer that card memory had the potential to serve as a data exchange medium that lacked the environmental vulnerability of floppy disks (such as LBLdust, temperature, shock, and impact).

While exploring marketing opportunities for his memory cards, Reimer discovered that the Poqet Computer Company was itself investigating the use of memory cards as an alternative to disk drives for a new product that was ultimately to become the first true sub-notebook PC. (Fujitsu had invested in the Poqet startup and has since acquired the company.) But Poqet was so concerned about the lack of standards among the various memory cards that it hesitated to select a memory card product because of uncertainty about which designs would succeed.

Sensible as was Poqet's desire to standardize memory cards throughout the industry, Reimer found that realizing the desire was a practical impossibility. No single standards organization was set up to rule on all the required aspects of such a design: physical card size, number and function of the connector pins, data file formats, and software interface. And to run all the different facets of a card design through the whole gamut of separate standards-sanctioning organizations might take longer than the useful life of the product.

While promoting the idea that the personal computer industry should itself develop a memory card standard, Reimer discovered that Lotus Development was contemplating putting its software on ROM cards. Lotus had been among the first to embrace putting software on the larger cartridges of the ill-fated PCjr. But Lotus, too, balked at the prospect of a profusion of incompatible card designs, and offered its support when Reimer proposed to bring parties interested in memory card standardization together. Reimer found enough initial support among other major suppliers of software, semiconductors, and personal computers, to convene a meeting of representatives from about 25 manufacturers that took place at the Fairmont Hotel in San Jose in June 1988.

That first informal meeting pointed out the possibilities-including the potential for an antitrust suit. So with $10,000 contributed by Fujitsu, Reimer hired lawyers to draft guidelines that would avert legal tangles and organized the group that became the Personal Computer Memory Card Industry Association or PCMCIA. At that early point, however, the role and future of the organization were uncertain. Early on, Reimer entertained the possibility that PCMCIA would craft a standard and quietly fade away, mission accomplished. But the organization gained its own momentum at its monthly meetings, and the standard expanded in scope from a PC enhancement to a universal digital data exchange mechanism.

In face of the rapid increases in peripheral performance brought by local bus interfaces, the original PCMCIA specifications look laggardly indeed. To keep in step with technology, the organization developed a new standard that incorporated the strengths of the local bus design. To distinguish the standards, PCMCIA now prefers to term its original, AT-bus based standard as PC Card and the local bus-based cards as CardBus. In addition, another industry group developed a smaller version of PCMCIA cards using a subset of its signals and restricted to memory operations. The resulting standard is termed Miniature Card.

PC Card

PC Card, Release 1.0, the first generation of the PCMCIA standard, was introduced in September 1990. It contemplated only the use of solid-state memory on the card as a means of data storage. But the PC Card intrigued both the makers of sub-notebook computers and peripheral developers, who believed that the standard could be expanded to incorporate I/O devices as well as memory.

As a result, the PC Card standard was updated in September 1991 to comprise a more generalized interface that would accommodate both storage and input/output devices. Additionally, the new Release 2.0 standard allowed the use of thicker cards, permitting the incorporation of a wider variety of semiconductor circuits. It also allowed programs stored on PC Cards to be executed in the card memory instead of requiring the code to be downloaded into standard RAM.

In keeping with good practice, backward compatibility was maintained: Cards designed under PCMCIA Release 1.0 plug into and work in Release 2.0 machines. Because Release 2.0 adds a wealth of features that older hardware may not understand, however, all the functions of a new card may not work in an older system. Because normal thickness cards of both generations are physically the same, new cards will fit slots in old systems. No combination of card and system will result in damage at either end of the connection.

Backward compatibility at that early stage was, of course, practically a non-issue. The only device limited solely to PCMCIA Release 1.0 form factor slots was the Poqet sub-notebook. Although the Hewlett-Packard 95LX conforms to Release 1.0 electrically, its socket accommodates the thicker cards permitted by Release 2.0.

The completed PCMCIA 2.0 is much more than a simple set of physical specifications for card dimensions and a bus pinout. The standard also describes file formats and data structures, a method through which a card can convey its configuration and capabilities to its host, a device-independent means of accessing card hardware and software links independent of operating systems.

CardBus

To bring the PC Card into the 32-bit world, PCMCIA adapted the highly regarded PCI expansion bus to the credit-card format in November 1994, to create the CardBus. Just as PC Card is a miniaturized version of ISA, CardBus shrinks down PCI while yielding the same high data transfer rates with one important exception: due to limitations in the connector design, CardBus extends only to a 32-bit bus width while the PCI standard allows for 64-bit buses. The reason for this constraint is, as usual, backward compatibility. CardBus cards are physically identical to PC Cards both in size and connections. You can slide either one into a slot and either kind of card will work in a PC that supports them.

Miniature Card

For memory applications where even a PC Card is too big, chip maker Intel developed an even smaller standard called, appropriately, Miniature Card, first released as version 1.0 on February 29, 1996. Envisioned as the perfect memory solution for digital cameras and miniaturized digital audio recorders, Miniature Cards are less than an inch and a half square but can store up to 64MB using any standard memory technology. In addition, the Miniature Card design is readily adaptable as a replacement for conventional memory modules, providing all the signals required for access as ordinary system memory.