CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [307]
Figure 18-14 Hubbed versus daisy chain connections
FireWire devices do use much more power than USB devices, but the FireWire controllers are designed to handle higher voltages, and they’ll warn you on the rare chance that your FireWire devices pull too much power.
General Port Issues
No matter what type of port you use, if it’s not working, you should always check out a few issues. First of all, make sure you can tell a port problem from a device problem. Your best bet here is to try a second “known good” device in the same port to see if that device works. If it does not, you can assume the port is the problem. It’s not a bad idea to reverse this and plug the device into a known good port.
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NOTE A “known good” device is simply a device that you know is in good working order. All techs count heavily on the use of known good devices to check other devices. For example, if you think a PC has a bad keyboard, borrow one from the PC next door and see if that keyboard works on the broken machine.
If you’re pretty sure the port’s not working, you can check a few things: Make sure the port is turned on. Almost any I/O port on a motherboard can be turned off in CMOS. Reboot the system and find the device and see if the port’s been turned off. You can also use Windows Device Manager to disable most ports. Figure 18-15 shows a disabled parallel port in Device Manager—you’ll see a small down-pointing arrow in Windows Vista/7 or a red X over the device icon if you are using Windows 2000/XP or. To turn the port back on, right-click the device’s icon and choose Enable.
Figure 18-15 Disabled parallel port in Device Manager in both Vista and XP
Being able to turn off a port in Device Manager points to another not-so-obvious fact: ports need drivers just as devices need drivers. Windows has excellent built-in drivers for all common ports, so if you fail to see a port in Device Manager (and you know the port is turned on in CMOS), you can bet the port itself has a physical problem.
Because ports have connectors inserted and removed from them repeatedly, eventually they can physically break. Figure 18-16 shows the back of a USB port that’s been pushed on too hard for too long and has physically separated from the motherboard.
Figure 18-16 Broken USB port
Unless you’re an expert solderer, you either must stop using those ports or replace the entire motherboard.
Figure 18-17 Badly bent PS/2 plug
Many ports (or the plugs that fit into those ports) use tiny pins or relatively delicate metal casings that are susceptible to damage. PS/2 plugs are some of the worst for bent pins or misshaped casings. Figure 18-17 shows what happened to a PS/2 plug when I was in a hurry and thought that force was an alternative to lining up the plug properly. Replacement plugs are available—but again, unless you’re excellent at soldering, they’re not a viable alternative. Still, if you’re patient, you might be able to save the plug. Using needle-nose pliers and a pair of scissors, I was able to reshape the plug so that it once again fit in the PS/2 port.
Common I/O Devices
So what is a “common” I/O device? I’m hoping you immediately thought of the mouse and the keyboard, two of the most basic, necessary, and abused I/O devices on a computer. Another fairly common input device that’s been around a long time is the scanner. To these oldsters, you can add relative newcomers to the world of common devices: digital cameras and Web cameras.
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NOTE If you want to get picky, these five common I/O devices enable a user only to input data; they don’t provide any output at all.
Keyboards
Keyboards