What is an Expresscard slot?

Most modern computers come with at least one USB socket that enables users to connect them to other devices. But before USB, the main way to add new functions to a laptop was to use the PC Card slot.

Its successor is the Expresscard slot, which is usually on one side of a laptop. We'll take a look at what it is and how you can use it.

The history
USB technology is relatively new; although it was invented in 1996 it has only been common on all computers in the past decade. Prior to that, users who wanted to add new features to desktop computers would open them up and plug a PCI card into an available PCI slot on the motherboard.

For laptops, where the motherboard was not easily accessible – and in any case there was no room in the case for large expansion cards – the industry came up with something new.

It was called PCMCIA, which stood for Personal Computer Memory Card International Association (though some wags claimed the lengthy abbreviation stood for People Can't Memorise Computer Industry Abbreviations).

The name was later changed to PC Card. A later variation of the technology was known as Cardbus, but we'll use PC Card to refer to both versions.

PC Cards were just over two inches (54mm) wide and a few millimetres tall. Originally, the cards were used to expand the hard disk space available to the laptop – it was cheap and easy to mount a hard disk on the PC Card or use the card as an adapter for an external disk.

They were also used to add modems or networking capabilities to computers. Later on, PC Cards were commonly used to add wireless network connections, and were even used for storage in early digital cameras.

What's it used for?
By 2005 the simpler and easier USB sockets had become common on most computers. They tended to be plug-and-play, which meant you could simply plug a device into a USB socket, install software if necessary, and start using it.

PC Cards, on the other hand, sometimes required complicated configuration. Also, USB devices are common on all computers, whereas PC Cards were largely restricted to laptops.

The answer to USB was the Expresscard, which was introduced in 2003 but didn't become common until a couple of years later. The main advantage of Expresscards is speed: the faster PCI-Express standard had by now replaced PCI on computer motherboards, and PC Cards were still using PCI while Expresscards used PCI Express.

Because of this direct connection to the computer's heart, Expresscards were also faster than USB connections.

Expresscards slots are smaller than PC Card slots, at just 34mm wide, though some PCs have a larger version that is just as wide as older PC cards and could accept both wider and narrower Expresscards.

Uses of the technology included fast network adapters, external hard disks (at faster speeds than were then possible over USB), TV tuners, sound cards, parental control systems, mobile broadband modems and more.