As the previous section illustrates, portable computers typically contain all the devices that users need to perform work away from the office; however, users have become accustomed to using additional items with their computers. For this reason, portables offer a wide range of I/O and expansion options to accommodate external FRU devices. The most common external devices used with portables include
External disk drives
External power sources and supplies
External I/O devices
Peripheral Storage Devices
With portable systems, external storage devices normally connect to one of the computer's PCMCIA slots, an I/O port connector, or a high-speed bus extension. Because portable units tend to be used with battery power, external storage devices also tend to employ separate, external power-supply units.
Several newer storage technologies, such as removable hard-drive media, have been designed to take advantage of the Type III PC-Card specification, or one of the new high-speed bus connections such as USB, FireWire, and SCSI ports. Some of these technologies are designed to use the portable's enhanced parallel port for connectivity with the system. These devices can be connected directly into the system's parallel port, or they can be connected to the system through another device that is connected to the port. The device's installation software is used to configure it for use with the system.
External Drive Units
The first laptops and notebooks incorporated the traditional single floppy-drive and single hard-drive concept that was typical in most desktop units. However, as CD-ROM drives and discs became the norm for new operating systems and software packages, a dilemma was created. Most notebook computers simply do not have enough room for three normal-size drive units. Even with reduced-size drives, the size limitations of most portables require that one of the three major drives be external.
Typically, the first item to be left out of a new notebook design is the internal floppy drive. So much of the latest software is distributed on CD-ROM that those drives now have preference in newer designs. Even so, so many applications still use floppies that an external FDD is almost always an add-on option for a new notebook. Large volumes of software are still available on floppies, and so many users have cherished data stored on floppies that an additional unit usually makes sense.
In some instances, portable manufacturers offer computer models that include interchangeable floppy and CD-ROM drive units for their units. Either of these drives can be installed in the portable system before starting it up. This arrangement prevents you from needing to purchase an extra component. It also keeps you from having to use one of the available PCMCIA slots for the floppy drive.
The external floppy comes as a complete unit with an external housing and a signal cable. As with other external devices, it requires an independent power source, such as an AC adapter pack. The external floppy drive's signal cable generally connects to a special FDD connector, such as the one shown in Figure 3.13.
Figure 3.13 An external floppy drive.
External CD-ROM Drives
Prior to the CD-ROM drive becoming an accepted part of the notebook PC, some manufacturers produced external CD-ROM drives for use with these machines. They are still available as add-ons to all types of PCs. External CD-ROM drives typically connect to a SCSI host adapter or to an enhanced parallel port. The latter connection requires a fully functional, bidirectional parallel port and a special software device driver.
Figure 3.14 illustrates the installation of an external SCSI CD-ROM drive. Because the drive is external, connecting the CD-ROM unit to the system usually involves simply connecting a couple of cables together. First, connect the CD-ROM's power supply to the external drive unit. Before making this connection, verify that the power switch, or power supply, is turned off. Connect the signal cable to the computer. Finally, connect the opposite end of the cable to the external CD-ROM unit. Complete the installation by installing the CD-ROM driver software on the system's hard-disk drive.
Figure 3.14 Installing an external CD-ROM drive.
External CD-RW and DVD-RW Drives
The installation process for external read/write CD-ROM and DVD drives is similar to installing external CD-ROM and DVD drives. These units connect to the system through a USB port, a FireWire port, an external SCSI connector, or a Cardbus adapter. Using these ports and buses, the system's PnP operation can detect any new hardware attached to the system when it is installed. However, most of the devices are nonstandard in nature and require that the OEM applications package be installed from the OEM CD that was packaged with the drive to control them.
In the Windows XP environment, read/write CD-ROM and DVD drives are supported directly from the operating system and don't require any third-party applications. When you insert a blank disc in one of these drives, the operating system detects it and pops up a dialog box that asks what you want to do with the disc. Most users still prefer to install a third-party program to manage all the functions of these drives.
As with desktop systems, removable storage associated with portable systems includes floppies, CDs/CD-RWs and DVDs/DVD-RWs, and tapes. However, the portable computer industry is much more advanced when it comes to removable storage systems. Popular removable storage systems associated with portable computers include solid-state USB drives and PC Card drives. The PC Card versions of removable storage can consist of either mechanical or solid-state disk drives.
USB memory drives automatically load USB drivers and simply function as another drive in the system (for example, drive D:). Likewise, with PC Card disk drives, the entire peripheral is PnP and hot swappable.
Installing External Storage Devices
The general procedure for installing external storage devices is as follows:
Configure the device for operation.
Refer to the device's user manual regarding any configuration jumper or switch settings.
Record the device's default configuration settings.
Set the device's configuration settings to operate at the default setting.
Install the device's PCMCIA adapter card (if necessary).
Install the PC Card in the PCMCIA slot. The system should detect the presence of the new card in the slot and automatically configure it for operation.
Make the device's external connections.
Connect the device's signal cable to the appropriate connector on the notebook, or the PC Card.
Connect the opposite end of the cable to the device.
Verify that the power switch or power supply is turned off.
Connect the power supply to the external storage unit.
Configure the device's software.
Turn on the system.
Check the CMOS setup to ensure that the port setting is correct.
Run the device's installation routine from the OEM disk or CD-ROM.
Portable Power Sources
Notebooks use detachable, rechargeable batteries and external power supplies, as illustrated in Figure 3.15. (Battery sizes vary from manufacturer to manufacturer.) They also employ power-saving circuits and ICs designed to lengthen the battery's useful time. The battery unit contains a recharging circuit that enables the battery to recharge while it is being used with the external power supply. Like other hardware aspects of notebook computers, there are no standards for their power-supply units.
Figure 3.15 Laptop/notebook power supplies.
Like other computer power-supply types, portable power supplies, also referred to as AC adapters, convert commercial AC voltage into a single DC voltage that the computer can use to power its components and recharge its batteries. Similar DC-to-DC controllers are available; they permit notebook computers to draw power from a DC source such as cigarette lighter sockets in automobiles. From manufacturer to manufacturer, however, these AC and DC power converters often employ different connector types and possess different DC voltage and current-delivery capabilities. Therefore, a power supply from one notebook computer does not necessarily work with another portable model.
When you are obtaining a replacement or accessory adapter or controller, the best choice is to get the suggested model from the notebook manufacturer. But if you must get these devices from a third party, match the output voltage level of the original. Also make certain that the replacement unit is capable of delivering at least as much current as the original supply.
Be aware that the external power supply used with portable systems basically converts AC voltage into DC voltage that the system can use to power its internal components and recharge its batteries.
Because the premise of portable computers is mobility, you can assume that it is able to run without being plugged into an AC outlet. The question for most portables is how long it will run without being plugged in. This is the point where portable designs lead the industry. They continuously push forward in three design areas:
Better battery design
Better power-consumption devices
Better power management
As mentioned earlier, power consumption consideration has been built into most devices intended for use with portable computers. Many of the Pentium chipsets provide a standby mode that turns off selected components, such as the hard drive and display, until a system event, such as a keyboard entry or a mouse movement, occurs. An additional power-saving condition, called suspend mode, places the system in a shut-down condition except for its memory units.
An additional power-saving mode, known as hibernate mode, writes the contents of RAM to a hard-drive file and completely shuts down the system. When the system is restarted, the feature reads the hibernate file back into memory, and normal operation is restarted at the place it left off.
Each sector of the portable computer market has worked to reduce power-consumption levels, including software suppliers. Advanced operating systems include power-management features that monitor the system's operation and turn off some higherpower-consumption items when they are not in use (standby mode) and switch the system into a lowpower-consumption sleep mode (suspend mode) if inactivity continues.
These modes are defined by a Microsoft/IBM standard called the Advanced Power Management (APM) standard. The hardware producers refer to this condition as green mode. The standard is actually implemented through the cooperation of the system's chipset devices and the operating system. Control of the APM system is provided through the BIOS's CMOS Setup utility, as described in Chapter 16, "CMOS RAM."
Most new portable computers possess a number of automatic power-saving features to maximize battery life. Some can be controlled through the Power menu of the Advanced CMOS Setup utility. If the Hard Disk Timeout value is set to 3 minutes, the Standby Timeout to 5 minutes, and the Auto Suspend value to 10 minutes, the following activities will occur:
The hard disk will spin down after 3 minutes of inactivity.
After 2 additional minutes of inactivity, the system will enter the standby mode.
After 10 additional inactive minutes, the system will store the hibernation file on the hard drive and enter suspend mode.
The user also can enter the suspend mode by pressing a key combination for those times when he or she must step away from the computer for a few minutes but does not want to shut down. The POWER.EXE command must be loaded in a Device= line of the CONFIG.SYS file for APM to work properly under DOS 6.x or Windows 3.x. This command is not needed to run APM in Windows 9x.
When the system suspends operation, the following events take place:
The video screen is turned off.
The CPU, DMA, clocks, and math coprocessor are powered down.
All controllable peripheral devices are shut down.
The amount of time the unit can remain in suspend mode is determined by the remaining amount of battery power. For this reason, data should be saved to the hard drive before voluntarily going to suspend mode. Pressing the computer's power button will return the system to its previous operational point.