The association's PC Card Standard provides physical specifications for three types of PC Cards, with additional provisions for extended cards. Each of the three card types measure the same length and width and use the same 68-pin connector. The only difference between the card types is thickness. The thicknesses are 3.3, 5.0, and 10.5 millimeters for Type I, Type II, and Type III cards respectively. Because they differ only in thickness, a thinner card can be used in a thicker slot, but a thicker card cannot be used in a thinner slot. The card types each have features that fit the needs of different applications. Type I PC Cards are typically used for memory devices such as RAM, Flash, OTP, and SRAM cards. Type II PC Cards are typically used for I/O devices such as data/fax modems, LANs, and mass storage devices. Type III PC Cards are used for devices whose components are thicker, such as rotating mass storage devices. Extended cards allow the addition of components that must remain outside the system for proper operation, such as antennas for wireless applications.
The release number refers to the version of the PC Card Standard that a particular card or system was based on. Basically, release 1.0 supported memory only, and 2.X releases supported memory and I/O applications.
PCMCIA Standard Release 1.0/JEIDA 4.0 - June 1990
The first release of the standard defined the 68-pin interface and the Type I and Type II PC Card form factors. The initial release of the PCMCIA Standard specified the electrical and physical requirements for memory cards only. It defined the Metaformat or Card Information Structure (CIS) that is critical to interoperability and plug-and-play for PC Cards. There was no concept of input/output (I/O) cards in the first release of the PC Card Standard.
PCMCIA Standard, Releases 2.0, 2.01 and 2.1 - 1991-1994
The second release of the standard defined an I/O interface for the same 68-pin interface as was used for the PCMCIA memory cards in the first release of the Standard. Release 2.0 also added various clarifications to the first release, support for dual-voltage memory cards, and sections dealing with card environmental requirements and test methods. Release 2.01 added the PC CardATA specification, the Type III card type, and the Auto-Indexing Mass Storage (AIMS) specification geared toward digital images was also added. It also included the initial version of the Card Services Specification. Release 2.1 further enhanced the Card and Socket Services Specification, and made improvements to the Card Information Structure.
PC Card Standard-February 1995
The latest release of the PC Card Standard added information to improve compatibility and added support for features such as 3.3-volt operation, DMA support, and 32-bit CardBus busmastering.