Using the Proprietary Expansion Bus

To save weight and space, portable computers do not use standard expansion bus designs, such as the ISA, PCI, or AGP expansion slots used on desktop computers. Instead, many (but not all) portable computers have proprietary connectors (see Figure 12.10) on the rear or bottom of the system case that will connect with either a docking station or a port replicator.

Figure 12.10. A typical notebook computer with Infrared serial port, SVGA video port, parallel port, and expansion bus for use with a docking station or port replicator (not shown). Dual folding doors, retracted here, protect the expansion bus from damage.

Docking Stations and Media Slices

A docking station expands the capability of a portable computer by adding features such as

• One or more ISA or PCI expansion slots

• Additional I/O ports, such as serial, parallel, PC Card, VGA, or USB

• Additional drive bays

• Connectors for a standard keyboard and mouse

Most docking stations are produced by the vendor of the notebook computer.

Docking stations are also used by PDAs, such as the Palm series and Pocket PC models. These computers use their docking stations primarily for data transfer or battery recharging.

Some thin and light portable computers are designed to use a modular media slice for optical and removable-media drives . This unit connects to the bottom of the computer and can be left in place at all times, or can be removed when not needed.

Configuring Docking Stations and Devices

A docking station doesn't require any special hardware configuration, but the devices attached to it often do.

tip

If in some devices the computer or the operating system doesn't support PnP (Windows NT 4.0 is not a PnP operating system), you can create an alternative hardware profile from the System properties sheet, Hardware Profiles screen. Using this feature requires you to manually enable and disable hardware features in the Docked profile you will create by copying the original configuration.

Windows 9x/Me/2000/XP use Plug and Play to support devices available to a portable computer when it is docked; the PnP devices are automatically detected and used.

Port Replicator

A port replicator usually connects to the same proprietary expansion bus that can be used by a docking station; many portable computers that do not have docking stations have optional port replicators.

Port replicators don't have expansion slots or drive bays but feature standard I/O ports (serial, parallel, VGA, and USB), keyboard, and mouse connectors. They enable a portable computer user fast, easy connection to a full- sized keyboard, regular mouse or pointing device, desktop VGA monitor, modem, and printer without needing to attach or remove multiple cables. Because portable cable connectors can wear out, using a port replicator extends the life of the system and makes desktop use faster and easier.

Some company systems use devices similar to conventional port replicators to provide access to the system's I/O ports; these systems provide just the expansion bus, without any normal ports, to save space and weight. This is true of very small portable systems such as the Toshiba Libretto series and others. In these cases, the port replicator is normally supplied with the system instead of being an optional extra.

Port replicators normally are built by the same company that makes the portable computer, but some third-party vendors produce both dedicated models (designed to attach to the proprietary expansion bus of a given model) and universal versions, which attach through the PC Card slot or USB port and can be freely moved among different brands and models of portable computers.

Software drivers are required for universal port replicators but not for standard port replicators.