PC card

V.34 data / fax modem -
PC card type II

WLAN CardBus card type II

PC Card is the current name of a standard for expansion cards for mobile computers ; Initially, these cards were known as PCMCIA cards , after the standards body at the time, the Personal Computer Memory Card International Association (PCMCIA).

PC cards are energy-saving and support hot-plug , so they can be changed during operation. Since all the card properties required for the automatic configuration of the driver are stored in the Card Information Structure (CIS) , plug and play is also possible.

development

The first standard developed by the standardization committee (PCMCIA Standard Release 1.0) was aimed at using PCMCIA cards as memory expansions and was adopted in 1990. As early as 1991, however, Release 2.0 of the specification was published, which now also contained protocols for using the PCMCIA card as a mobile data storage device and for providing communication interfaces. Finally, in 1993, the specifications for Release 2.1 were revised again.

With the introduction of the CardBus standards (PC Card Standard 5.0) 1995 PCMCIA cards were first officially as a PC card (ger .: PC Card ), respectively. In the meantime, the term PC Card has established itself simply because it is easier to market than the abbreviation PCMCIA.

The PC card standard has so far defined three different sub-standards:

PC Card 16: 8 or 16 bit data bus. The data rates that can be achieved with this card type correspond roughly to those of 16-bit ISA cards (approx. 16 Mbyte / s). These cards can be operated with 5 or 3.3 volts .
CardBus: 32-bit data bus. Compared to PC Card 16, they have an additional, mostly golden contact strip on the top. The protocol of CardBus cards is based on PCI, the bus clock is 33 MHz and is therefore comparable with PCI cards (max. 132 Mbyte / s). CardBus cards are always operated with 3.3 volts. They allow bus mastering , which reduces the load on the processor during data transfer.
CardBay: an extension of the PCMCIA specification from 2001. They wanted to create compatibility with USB and IEEE 1394 (FireWire) , but the project was not fully implemented. Instead, the development of the ExpressCard was intensified. There are only a few notebooks (with controllers from TI or O2Micro) that support CardBay.

Design

There are three different designs, all measuring 85.6 mm × 54.0 mm, but differing in their thickness:

Type I (3.3 mm) is used for memory cards with SRAM or Flash . Pure type I slots can be found in confined spaces.
Type II (5.0 mm) is mainly used for modems , network cards, etc. These are the most common slots.
Type III (10.5 mm) was originally required for pluggable hard disks , but these became obsolete due to advancing miniaturization and were hardly ever more common. However, the greater height makes it possible to accommodate connections directly in the card housing - thus also flush with the notebook housing - so that a fragile adapter cable is unnecessary. Many more modern devices no longer contained explicit Type III slots.
Current notebooks usually come with the successor ExpressCard at most , although its popularity is already decreasing.

compatibility

Above a Type III card for 3.3 V, below for 5 V

Differences between a PC Card 16 card (left) and a CardBus card (right)

The technology is fully downward compatible . Slots for CardBus cards can also operate 16-bit cards, but not the other way around. Type II slots also accept Type I, but not Type III cards. However, two type II slots are often available, one above the other, so that a type III card can be inserted into the lower slot, which also occupies the space available in the upper slot.

The voltage required for a card is coded via a recess on the right side of the front side. This prevents 3.3 volt cards from being operated in slots that only supply 5 volts. 5-volt cards could also be inserted into slots that are suitable for 3.3-volt cards, but the card driver will not switch on the voltage. Some cards can be operated on 5-volt and 3.3-volt slots - i.e. with both voltages.

With a suitable adapter, PC cards 16 can also be used in a CompactFlash slot. There is currently no way to use a CardBus card in a standard PDA . But there are a few PDAs with a PC card interface. Notebooks manufactured in 1999 or later are usually equipped with CardBus slots.

PCMCIA adapter for PCI bus

PC card adapters for the PCI bus are available for desktop computers . These implement the slot via a plug-in card with a separate PCI PC card controller, but in most cases do not support hot-plugging.

PC Card and the successor ExpressCard

As the successor to the 32-bit PC card, the PCMCIA developed the ExpressCard under the code name NEWCARD .

These are available as ExpressCard / 34 (34 × 75 mm, 5 mm thick) and ExpressCard / 54 (54 × 75 mm, 5 mm thick, the connection corresponds to the ExpressCard / 34, so this model has an L-shape).

An ExpressCard / 34 is almost half the size of a previous generation PC card. It can use both the internal USB 2.0 interface (480 Mbit / s = 60 Mbyte / s) and the PCI Express 1x interface (1 lane). PCI Express works at 2500 Mbit / s in each direction , which corresponds to 250 Mbyte / s because of the 8b10b coding . A PC Card 32 comes to 1066 Mbit / s (133 Mbyte / s). This means that the ExpressCard is about twice or even four times as fast when a duplex transmission is achieved.

ExpressCards are not backwards compatible with normal PC Cards. Such cards cannot easily be operated in conventional CardBus slots or existing PC cards or CardBus cards in an ExpressCard slot. However, there is an ExpressCard to PC Card bridging adapter that enables this.

There are also adapters - among others from various cell phone providers - to operate data cards in ExpressCard / 34 format and with a USB interface in a PC card slot. These contain an interface converter. Cards with a native PCI Express interface (such as Gigabit Ethernet, eSATA , FireWire) are not supported by such adapters.