ExpressCard combines a small removable form factor, currently aimed at laptops, with x1 PCI Express and USB 2.0 standards (see "ExpressCard: Changing The Face Of Computing" at www.elecdesign.com, ED Online 6608). Hosts must support both interfaces, but the ExpressCard device typically uses only one.
PCI Express eventually will flow into the ExpressCard mainstream, but USB 2.0 dominates for now. In fact, at this point, only a few products will use PCI Express. This isn't too surprising, though, because migration of existing USB external devices to ExpressCard is a straightforward design task. USB even finds its way into video applications. PCI Express support should find a home in Gigabit Ethernet adapters, all the while keeping an eye on the race between plug-in and built-in support.
