CardBus

The PCMCIA (Personal Computer Memory Card International Association) has enhanced the performance of the original 16-bit PCMCIA interface. The new standard for 32-bit data transfers, known as CardBus, is designed to give PCI-like performance to laptops and opens up a wide range of currently unavailable applications to mobile users.

What is CardBus ?

CardBus is defined in the latest revision of the PC Card standard (2.1), and is designed to accommodate the anticipated move to PCI local bus notebooks from the slower VL-bus based systems.

This new standard was developed around the established PCI bus specification and allows 32-bit devices to be packaged in a similar form-factor to 16-bit PCMCIA cards.

CardBus, like PCI, uses a 32-bit data bus running at 33MHz maximum; however, instead of the 108 pin-interface of PCI, CardBus has only 68 pins. This allows a CardBus slot to offer backward compatibility with existing 16-bit PCMCIA cards, thus providing the user with a smooth upgrade path without the need to replace existing cards.

The Benefits of CardBus

The trend in the mobile PC market is toward duplicating the office environment. CardBus will enable the migration of most high performance functions, currently only available on desktop and larger systems, to the mobile environment.

With the predicted move to PCI based notebooks, it is possible that existing PCMCIA network cards may prove to be a performance bottleneck. CardBus addresses this issue by operating at up to six times faster than the Release 2.1 PCMCIA interface.

Potential CardBus Applications

Currently several applications are not possible in the mobile environment because of bandwidth restrictions. A few examples are :

High Performance Networking

As the graphical nature of interactive applications grows so will the demand for high performance network access for mobile platforms. With a burst rate of 132Mbytes/sec CardBus can easily accommodate these requirements, and provides substantial bandwidth for future multi-media business applications.

Image Capture and Video

Early applications will centre around low-end multimedia, making it possible to exchange digital audio and visual information remotely.

Simultaneous Voice and Data

Although CardBus may be inappropriate for full screen / full motion video, it is well suited to white board conferencing where stationary images are altered and discussed simultaneously.

Madge Position

Madge Networks is currently evaluating the benefits of CardBus for next generation network adapters, and is considering development of a high performance CardBus Token Ring adapter to enable the user to fully exploit the features of new CardBus notebooks.

CardBus Features

Coexistence with modems in multi-slot machines
Software configurable (Plug & Play compatible)
Hot insertion support
Advanced power management functions, including support for slow or stopped clocks and also for system suspend/resume commands
Bus Mastering - reducing CPU utilization and facilitating the move to multiprocessor-based distributed intelligence
32-bit address/data bus at 32MHz
3.3v operating voltage
Auto ring speed detect

Madge recognizes that an important issue for the customer with any PC Card product is the strength and reliability of the network cable and connector.

As part of a continual effort to further improve the quality of products offered by Madge, consideration is being given to the design of a custom connector to our own specification. This connector will be required to have strength, a true latching mechanism, and the ability to coexist without interfering with the X-jack connectors used on many modem cards.

Compatibility

Madge is a registered member of the industry association Yenta, organized by Intel, whose aim is to eliminate the types of compatibility issues that hindered the adoption of 16-bit PCMCIA technology. Through Yenta, Madge is taking a pro-active approach to ensure maximum compatibility across a wide range of PC vendor platforms, BIOS's, Card and Socket Services and operating systems.

Madge is also co-operating with Compaq under their PC Card Solutions Program, and non-disclosure agreements have been entered into with various other PC and Card Controller vendors.

History of PCMCIA

Originally intended only for memory cards, the first release of the PCMCIA Standard was published in June 1990, and was defined by the Japan Electronic Industry Development Association (JEIDA).

With the introduction of PCMCIA Standard Release 2.0 in September 1991, I/O cards were supported for the first time across the same 68-pin interface used by memory cards. In this release, support was also added for dual-voltage cards, and the Card Information Structure (CIS) - defined in the first release - was enhanced.

November 1992 saw the introduction of PCMCIA Standard Release 2.01. To accommodate hard disk PC Cards, the Type III Card was added and the initial version of the Card Services specification was defined. Socket Services were enhanced to accommodate the new Card Services interface and changes were made to the CIS to support new PC Card functionality.

In July 1993, the latest version of the PCMCIA Standard was introduced, Release 2.1. The Card and Socket Services specifications were enhanced to strengthen compatibility and the CIS was updated again.

The PC Card Standard was published by PCMCIA in February 1995, and - in an effort to further improve compatibility - every PC Card was now required to have a CIS. Support was also added for the following optional features: 3V low-voltage only cards, DMA, multiple-function cards and a power management interface.