CardBus is the current generation, high-performance 32-bit/bus master interface for PCMCIA slots in laptops. It provides the opportunity for migration of most high performance functions available on desktop and larger systems to CardBus cards for use in the mobile environment. New functions developed for CardBus may also be used in 32-bit desktop systems, if they are equipped with CardBus sockets.
CardBus is an extension of current PC Card software capabilities. All CardBus sockets must be able to accept and operate PC Card not utilizing CardBus within the capabilities of the system. Since all CardBus sockets also support non-CardBus cards, the initiative for implementation lies with the system developers. Once CardBus sockets are available on 32-bit systems, CardBus cards will be developed to take advantage of the performance provided by the 32-bit system.
CardBus is a higher performance version of a PCMCIA card. CardBus also offers lower power consumption: CardBus Cards are all 3.3-volt cards, while 16-bit PCMCIA Cards can be 5-volt or 3.3-volt. The key difference is the data path interface. 16-bit PCMCIA Cards are based on a 16-bit “ISA-like” interface, while CardBus Cards use a 32-bit “PCI-like” interface. This allows the CardBus Card to transfer data at speeds exceeding 100 Mbps, while a 16-bit PCMCIA card transfers data at approximately 20 Mbps. One way to conceptualize the relationship is to say that CardBus Card is to 16-bit PCMCIA Card as PCI is to ISA.
Conclusion: Cardbus slots accept both older 16-bit and newer 32-bit cards but the older PCMCIA slots only accept the 16-bit cards, not Cardbus cards.
More information: http://www.pc-card.com/papers/cardbus.htm
(Some) PCMCIA Dlink Cards ( see DlinkCardComments ) use a CardBus interface. See the different Bus types on the HardwareComparison page.
Q: Is this a good or bad thing?
A: Well, if you are using a ISA pcmciaBridge, then this is bad, as most of them don't support cardbus. But, it could be a little faster.... (but 11mbit is not really going to overload a 16bit slot, so your milage may vary).
Most older laptops have the original 16-bit PCMCIA slots. For older laptops from 1996 or older, if it doesn't say CardBus or have a little [CB] logo near the slot, it's probably 16-bit. Generally, laptops of 1999 or newer have Cardbus pcmcia slots. Caveat Emptor! Most products that require CardBus don't say so in very big letters on the package. You'll find that this is the case with USB PCMCIA cards too, there's no way to add USB ports to an older laptop that doesn't have CardBus slots. (But if it's new enough to have CardBus, chances are it has USB as well!)
I use non-CardBus ethernet cards in my laptops (because they are cheap) and the most annoying thing compared to a CardBus enabled card is the CPU utilization: 100% even on a 1ghz pIII-M with a 16bit card (@ 10mbit/s), compared to virtually 0% when using a 32bit card (@ 100mbit/s). These numbers are not tested, but only experienced values - so don't hang me if they are not 100% accurate! -- nikee_at_lux.wox.org
One way to conceptualize the relationship is to say that CardBus Card is to 16-bit PCMCIA Card as PCI is to ISA. ISA and PCI use completely different slot styles, I think it'd compare better between the 8bit ISA and 16bit ISA as both 16bit ISA and CardBus are upgrades with more pins. -- mage_at_shadowmage.org
