What is an ExpressCard?

With the announcement of the MacBooks, one of the features that Apple lists is the "ExpressCard/34". Unless you are into hardware, you probably haven't heard too much about the ExpressCard, because it's relatively new, and the use of ExpressCards relies on three pieces of technology that until very recently haven't been assembled together -- the right chipset, PCI Express architecture and ExpressCard.
What is an ExpressCard/34?


The ExpressCard is a way of getting a PCI-Express expansion slot onto a laptop. It's a new format of I/O device card designed to replace the PC Cards of yesteryear.
How fast is an ExpressCard?

It's much faster, theoretically capable of a throughoutput of 500MBps (250MBps in each direction) when compared to the PC Card (132MBps) The speed of the ExpressCard makes it ideal for doing data transfer without compression (useful for harddrives and other detachable media devices). For comparisson, USB 2.0 is 60MBps, Firewire 800 is 100MBps, Gigabit Ethernet is 125MBps.
What else is new in an ExpressCard?

There's two formats for ExpressCards at this moment, the ExpressCard/34 with a width of 34 mm and the ExpressCard/54 with a width of 54mm. Unlike the PC Card, instead of relying on an ejection button, the ExpressCard sticks out a little bit so one can just pull it out with their fingers.
What can we see in the future for ExpressCard?

I expect to see ExpressCard addons to include HDTV tuners (HDTV quality video display would choke a PC Card) and as the replacement for the PC Card, so we can expect to see any device produced for the PC Card to make its way onto the ExpressCard as well. Already available are some memory card readers and network adapters.