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In computing, PC Card (originally PCMCIA) is the form factor of a peripheral interface designed for laptop computers. It was originally for memory expansion, but the existence of a usable general standard for notebook peripherals led to all manner of devices being made available in this form. Typical devices include network cards, modems and hard disks, and even mice, such as the MoGo Mouse BT.
Many notebooks in the 1990s came with two Type II slots with no barrier in between (allowing two type II cards or one type III card). With the removal of legacy ports, most modern notebooks only feature one Type II card slot.
PCMCIA modules (or devices) were designed by the US computer industry to compete with the Japanese JEIDA memory card devices. The two standards later merged as JEIDA 4.1 or PCMCIA 2.0 (PC Card) in 1991.
Name
PCMCIA stands for "Personal Computer Memory Card International Association". While this acronym did clearly describe the organizations initial intentions it was difficult to say and remember and was sometimes jokingly referred to as "People Can't Memorize Computer Industry Acronyms" . To aid in the widespread marketing and branding of the standard and to account for the standards widening scope (beyond just memory cards) the association acquired the rights to simpler term "PC Card" from IBM and began using it (rather than "PCMCIA") from version 2 of the specification onward.
Card types
All PC Card devices use an identical 68 pin dual row connecting interface. All are 85.6 mm long and 54.0 mm wide. The form factor is also used by the Common Interface form of Conditional Access Modules for DVB broadcasts. The 16 mm thick "Type IV" card, introduced by Toshiba, was not officially sanctioned by the PCMCIA.
The original standard was defined for both 5 volt and 3.3 volt cards. The 3.3 V cards have a key on the side to protect them from being damaged by being put into a 5 V-only slot. Some cards and some slots operate at both voltages as needed. The original standard was built around an 'enhanced' 16-bit ISA bus platform.
Type I
The original specification cards (version 1.x) are Type I and feature a 16 bit interface. They are 3.3 mm thick. Type I PC Card devices are typically used for memory devices such as RAM, Flash, OTP, and SRAM cards.
Type II
The Type II PC Card devices feature a 16 or 32 bit interface. They are 5.0 mm thick. Type II cards introduced I/O support, allowing devices to attach an array of peripherals or to provide connectors/slots to interfaces for which the PC/laptop had no built-in support. For example, many modem, network and TV cards use this form factor. Due to their thinness, most type II interface cards feature miniature interface connectors on the card which are used together with a dongle; a short cable that adapts from the card's miniature connector to an external full-size connector.
Type III
The Type III PC Card devices are 16 or 32 bit. These cards are 10.5 mm thick, allowing them to accommodate devices with components that would not fit type I or type II height. Examples are hard disk drive cards, and interface cards with full-size connectors that do not require dongles (as is commonly required with type II interface cards).
Type IV
Type IV is not an official standard, though some devices come in this format.
CardBus
CardBus are PCMCIA 5.0 or later (JEIDA 4.2 or later) 32-bit PCMCIA devices, introduced in 1995 and present in laptops from late 1997 onward. CardBus is effectively a 32-bit, 33 MHz PCI bus in the PC Card form factor. CardBus includes bus mastering, which allows a controller on the bus to talk to other devices or memory without going through the CPU. Many chipsets are available for both PCI and CardBus, such as those that support Wi-Fi.
The notch on the left hand front of the device is slightly shallower on a CardBus device, so a 32-bit device cannot be plugged into a slot that can only accept 16-bit devices. Most new slots are compatible with both CardBus and the original 16-bit PC Card devices.
The speed of CardBus interfaces in 32 bit burst mode depends on the transfer type; in byte mode it is 33 MB/s, in Word mode it is 66 MB/s, and in DWord mode it is 132 MB/s.
CardBay
CardBay is a variant added to the PCMCIA specification in 2001. This was intended to add some forward compatibility with USB and IEEE 1394, but was not universally adopted and only some notebooks support CardBay features in their PC Card controllers.
Descendants and variants
The interface has spawned a generation of flash memory cards that set out to improve on the size and features of Type I cards: CompactFlash, MiniCard and SmartMedia. For example, the PC Card electrical specification is also used for CompactFlash, so a PC Card CompactFlash adapter need only be a socket adapter.
ExpressCard is a later specification from the PCMCIA, intended as a replacement for PC Card, built around the PCI Express standard. PC Card Standard is closed to further development and PCMCIA strongly encourages future product designs to utilize the ExpressCard interface. As of 2007, the majority of laptops now ship with only ExpressCard slots or neither slot type (leaving expansion to USB and Firewire only), though the Lenovo Thinkpad T60, among other models, currently ships with both CardBus and ExpressCard slots.
There is no general backward or forward compatibility between ExpressCard and CardBus sockets. CardBus devices do not fit ExpressCard sockets and ExpressCard devices do not fit CardBus sockets. Because of the differences in the interfaces, there are no general purpose adapters possible between the two formats. Some ExpressCard devices that use only USB technology could operate in CardBay compliant CardBus sockets with a suitable physical format adapter.
Card Information Structure
The Card Information Structure (CIS) is information stored on a PC card that contains information about the formatting and organisation of the data on the card.[1] The CIS also contains information about:
- The type of card
- Supported power supply options
- Supported power saving features
- The manufacturer
- Model number
- and so on.
When a card is unrecognised it is frequently because the CIS information is either lost or damaged.