In an effort to give notebook computers the kind of expandability users have grown used to in desktop systems, the Personal Computer Memory Card International Association (PCMCIA) established several standards for credit cardsize (and smaller) expansion boards that fit into small slots found in laptop and other portable computers such as Tablet PCs. These slots are designed to be externally accessible so that the cards can be quickly inserted and removed without opening up the system. They are also designed to be hot-puggable, meaning they can be inserted or removed with the system running. PCMCIA was founded in 1989 as a non-profit trade association to establish technical standards for PC Card technology. Originally, the PCMCIA also worked with Japan Electronic Industry Development Association (JEIDA) on some of the earlier standards, and currently PCMCIA has more than 200 member companies worldwide. The development and evolution of the PCMCIA's PC Card and new ExpressCard standards have proven to be successful in a market notorious for proprietary designs. The words "Memory Card" in the PCMCIA name allude to the original 1.0 specification it released in September 1990, which was for memory cards only. The 2.0 release that came in September 1991 added support for input/output (I/O) cards as well. Subsequent releases have enhanced the standard further, adding higher performance modes, lower power consumption, and greater compatibility. While the original PCMCIA standard was based on the 16-bit AT-bus (also called ISA for Industry Standard Architecture), the latest ExpressCard standard is based on the high-speed PCI Express serial bus found in the latest desktop systems, as well as USB 2.0. Over the years from PCMCIA cards to PC Cards (CardBus) and ExpressCards, expansion cards for laptops have grown well beyond their simple memory card origins. Table 8.1 shows the history of PCMCIA, PC Card, and ExpressCard standards and revisions. Table 8.1. PCMCIA, PC Card, and ExpressCard RevisionsStandard | Date Released | Major Features/Changes |
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PCMCIA 1.0 (JEIDA 4.0) | June 1990 | Based on 16-bit AT-bus (ISA) 68-pin memory-only interface Type I/II form factors Card Information Structure (CIS) defined | PCMCIA 2.0 (JEIDA 4.1) | September 1991 | PC Card name adopted I/O interface added Dual-voltage memory card support Environmental requirements Socket Services API specification Enhanced Metaformat (geometry and interleaving tuples added) XIP (eXecute In Place) spec. added | PCMCIA 2.01 | November 1992 | PC Card ATA specification Type III form factor Auto-Indexing Mass Storage (AIMS) specification Card Services API specification Enhanced Socket Services support Enhanced Metaformat | PCMCIA 2.1 (JEIDA 4.2) | July 1993 | Card and Socket Services enhanced Electrical and physical spec. enhanced Enhanced Metaformat | PC Card 5.0 | February 1995 | 32-bit CardBus added, based on PCI CIS (Card Information Structure) required Low voltage (3.3V) only operation Hardware DMA support Advanced Power Management (APM) added Multi-function cards Guidelines document added | PC Card 5.01 | March 1995 | General editorial changes | PC Card 5.02 | May 1995 | Electrical spec. editorial changes | PC Card 5.03 | November 1995 | Support for custom interfaces added | PC Card 5.04 | March 1996 | Zoomed Video support added Flash Translation Layer (FTL) | PC Card 6.0 | March 1997 | Thermal ratings system ISDN, Security, and Instrumentation Card Tuples Hot Dock/Undock support Streamlined configuration | PC Card 6.1 | April 1998 | PCI power management Small PC Card form factor Win32 Socket Services bindings | PC Card 7.0 | February 1999 | PC Card memory paging Digital Video Broadcast (DVB) interface WinNT 4.0 Kernel mode Socket Services bindings | PC Card 7.1 | March 2000 | OpenCable POD interface support | PC Card 7.2 | November 2000 | Removal of DMA support Zoomed Video port register model Updated PC Card ATA spec. Limited host guidelines | PC Card 8.0 | April 2001 | CardBay USB interface Vcore supplemental voltage added | PC Card 8.1 | 2003 | Dedicated LPC (Low Pin Count) interfaces | ExpressCard 1.0 | September 2003 | PCI Express and USB 2.0 combined ExpressCard/34 and 54 form factors | Note: A tuple gives a set of things that participate in a relation between those things. For example, John and Jane can be linked by the marriage relation and classified as the tuple (John, Jane). |
The following sections discuss these expansion card buses in further detail. |