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PCMCIA (Personal Computer Memory Card International Association) was established in 1989 as a 'standards' body and trade association consisting of manufacturers of semiconductors, connectors, peripherals, systems, devices and software developers.
In the search for smaller and lighter (more portable) tools for expanding the power of the personal computer designers have been cutting down the size of expansion cards and peripheral devices for years. Instead of the traditional 16bit "full" slot ISA cards that have been used in PCs for many years the PCMCIA standards are promoting expansion devices that can be as small as a creditcard.
Some of the devices available and in the testing phases are Hard Disk Drives,network adapter cards, SCSI adapters and of course - modems. The designations for the PCMCIA cards as Type I, Type II and Type III are size indicators. Type I devices are the thinnest (3.3 mm thick) and are primarily used for memory devices like flash ram.
Type II cards are 5mm thick and modems and Lan adapters are the most common of these type.
Type III cards are 10.5mm and are used for the devices that require more space (more ICs needed for the card) such as disk drives and wireless communication devices.
The sizing is important when considering the computer you wish to purchase. A Type III slot can accept a Type I or Type II card in addition to the Type III. However, a Type II slot will only be able to accept a Type I and Type II. Toshiba has produced a slot slightly larger than the specs for the Type III (16mm) in anticipation of larger devices under development. In every other aspect the PCMCIA slots in the Toshiba computer adhere to the standards - otherwise we couldn't designate them as such.
In addition to the Type designation there is also a Version indicated for the standard specifications that were adhered to in the design of the device. The first spec was version 1.0 released in September 1990 with only hardware addressed. The second release was version 2.0 issued September of 1991. This version added software specs for input/output cards like modems and hard drives. Release 2.01 contains typographical corrections and no new technical specs.
Some of what the specs cover include the hardware configurations for pin assignments (they all have 68 pins), some electrical specifications and the ability to detect the insertion and removal of the cards to promote "hot swapping".
Software standards include the basic MS-DOS FAT (file allocation table) system on ROM and Ram memory cards as well as hard disk drives.
Typically a device driver is needed to manage the card - providing different levels of services within the standards. Each card contains a "Tuple" (software header) that identifies its electrical capabilities and logical status (type of card) tyo the system it is inserted into.