In a tower system, which of the following should be done before removing the system board?

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The exact steps required to replace a motherboard depend on the specifics of the motherboard and case, the peripheral components to be connected, and so on. In general terms, the process is quite simple, if time-consuming:

• Disconnect all cables and remove all expansion cards from the current motherboard.

• Remove the screws that secure the old motherboard and remove the motherboard.

• If you are reusing the CPU and/or memory, remove them from the old motherboard and install them on the new one.

• Replace the old back-panel I/O template with the template supplied with the new motherboard.

• Remove and install motherboard mounting posts as necessary to match the mounting holes on the new motherboard.

• Install the new motherboard and secure it with screws in all mounting hole positions.

• Reinstall all of the expansion cards and reconnect the cables.

The devil is in the details. In the rest of this section, we'll illustrate the process of installing the motherboard and making all the connections properly.

Before you start tearing things apart, make sure you have at least one good backup of all your important data. You needn't worry about backing up Windows and applications—although you should, if possible, back up the configuration information for your mail client, browser, and so on—because unless you're replacing an old motherboard with an identical new motherboard, you may need to reinstall Windows and all applications from scratch.

Disconnect all cables and external peripherals from the system, and move it to a flat, well-lighted work area—the kitchen table is traditional, as we mentioned earlier. If you haven't cleaned the system recently, give it a thorough cleaning before you begin work.

Remove the access panel(s) from the case, disconnect all of the cables from the motherboard, and remove all of the screws that secure the motherboard to the case. Ground yourself by touching the power supply. Slide the motherboard slightly toward the front of the case, lift it straight out, and place it aside on the table top or another nonconductive surface.

Removing the motherboard may expose more dirt. If so, use a brush and vacuum cleaner to remove that dirt before you proceed further.

Every motherboard comes with a back-panel I/O template. Unless the current template matches the port layout on the new motherboard, you'll need to remove the old template. The best way to remove an I/O template without damaging it (or the case) is to use a screwdriver handle to press gently against the template from outside the case, while using your fingers to support the template from inside the case until the template snaps out. If the old motherboard is still good, put the old template with it for possible use later.

Compare the new I/O template with the back-panel I/O ports on the new motherboard to make sure they correspond. Then press the new template into place. Working from inside the case, align the bottom, right, and left edges of the I/O template with the matching case cutout. When the I/O template is positioned properly, press gently along the edges to seat it in the cutout, as shown in Figure 4-15. It should snap into place, although getting it to seat properly sometimes requires several attempts. It's often helpful to press gently against the edge of the template with the handle of a screwdriver or nut driver.

Figure 4-15. Press the new I/O template into place

After you install the I/O template, carefully slide the motherboard into place, making sure that the back-panel connectors on the motherboard are firmly in contact with the corresponding holes on the I/O template. Compare the positions of the motherboard mounting holes with the standoff mounting positions in the case. One easy method is to place the motherboard in position and insert a felt-tip pen through each motherboard mounting hole to mark the corresponding standoff position beneath it.

Remove any unneeded brass standoffs and install additional standoffs until each motherboard mounting hole has a corresponding standoff. Although you can screw in the standoffs using your fingers or needlenose pliers, it's much easier and faster to use a 5 mm nut driver, as shown in Figure 4-16. Tighten the standoffs finger-tight, but do not overtighten them. It's easy to strip the threads by applying too much torque with a nutdriver.

Figure 4-16. Install a brass standoff in each mounting position

Once you've installed all the standoffs, do a final check to verify that each motherboard mounting hole has a corresponding standoff, and that no standoffs are installed that don't correspond to a motherboard mounting hole. As a final check, we usually hold the motherboard in position above the case, as shown in Figure 4-17, and look down through each motherboard mounting hole to make sure there's a standoff installed below it.

Figure 4-17. Verify that a standoff is installed for each motherboard mounting hole and that no extra standoffs are installed

If you have not already installed the processor and memory on the motherboard, do so before proceeding. See Chapters 5 and 6 for detailed instructions.

Slide the motherboard into the case, as shown in Figure 4-18. Carefully align the back-panel I/O connectors with the corresponding holes in the I/O template, and slide the motherboard toward the rear of the case until the motherboard mounting holes line up with the standoffs you installed earlier. You may need to tilt the motherboard slightly down towards the I/O template to slip the back-panel connectors easily under their corresponding grounding tabs without damage. Make absolutely certain that none of the grounding tabs intrude into the jacks on the I/O panel. USB ports are particularly prone to this problem, and a USB port with a grounding tab stuck into it might short out the motherboard and prevent the system from booting.

Figure 4-18. Slide the motherboard into position

Before you secure the motherboard, verify that the back-panel I/O connectors mate properly with the I/O template, as shown in Figure 4-19. The I/O template has metal tabs that ground the back-panel I/O connectors. Make sure that none of these tabs intrude into a port connector. An errant tab at best blocks the port, rendering it unusable, and at worst might short out the motherboard.

After you position the motherboard and verify that the back-panel I/O connectors mate cleanly with the I/O template, insert a screw through one mounting hole into the corresponding standoff, as shown in Figure 4-20.

Figure 4-19. Verify that the back panel connectors mate cleanly with the I/O template

You may need to apply pressure to keep the motherboard positioned properly until you have inserted two or three screws.

If you have trouble getting all the holes and standoffs aligned, insert two screws at opposite corners but don't tighten them completely. Use one hand to press the motherboard into alignment, with all holes matching the standoffs. Then insert one or two more screws and tighten them completely. Finish mounting the motherboard by inserting screws into all standoffs and tightening them.

Figure 4-20. Install screws in all mounting holes to secure the motherboard

Once the motherboard is secured, the next step is to connect the front-panel switch and indicator cables to the motherboard. Before you begin connecting front-panel cables, examine the cables. Each connector should be labeled descriptively—for example, "Power," "Reset," and "HDD LED." (If not, you'll have to trace each wire back to the front of the case to determine which switch or indicator it connects to.) Match those descriptions with the front-panel connector pins on the motherboard to make sure you connect the correct cable to the appropriate pins. Figure 4-21 shows typical pinouts for the Power Switch, Reset Switch, Power LED, and Hard Drive Activity LED connectors.

Figure 4-21. Typical front panel connector pinouts (image courtesy of Intel Corporation)

• The Power Switch and Reset Switch connectors are not polarized, and can be connected in either orientation.

• The Hard Drive Activity LED is polarized, and should be connected with the ground (usually black) wire on Pin 3 and the signal (usually red or white) wire on Pin 1.

• Many motherboards provide two Power LED connectors, one that accepts a 2-position Power LED cable and another that accepts a 3-position Power LED cable with wires in positions 1 and 3. Use whichever is appropriate. The Power LED connectors are usually dualpolarized, and can support a single-color (usually green) Power LED or a dual-color (usually green/yellow) LED.

Once you determine the proper orientation for each cable, connect the Power Switch, Reset Switch, Power LED, and Hard Drive Activity LED, as shown in Figure 4-22. Not all cases have cables for every connector on the motherboard, and not all motherboards have connectors for all cables provided by the case. For example, the case might provide a speaker cable, but the motherboard might have a built-in speaker and no connection for an external speaker. Conversely, the motherboard might provide connectors for features, such as a Chassis Intrusion Connector, for which no corresponding cable exists on the case; those connectors go unused.

Figure 4-22. Connect the front-panel switch and indicator cables

When you're connecting front-panel cables, try to get it right the first time, but don't worry too much about getting it wrong. Other than the power switch cable, which must be connected properly for the system to start, none of the other front-panel switch and indicator cables is essential, and connecting them wrong won't damage the system. Switch cables—power and reset—are not polarized. You can connect them in either orientation, without worrying about which pin is signal and which ground. If you connect an LED cable backwards, the worst that happens is that the LED won't light. Most cases use a common wire color, usually black, for ground, and a colored wire for signal.

Most cases provide one or two frontpanel USB 2.0 ports, and most motherboards provide corresponding internal USB connectors. To route USB to the front panel, you must connect a cable from each frontpanel USB port to the corresponding internal connector. Figure 4-23 shows the standard Intel pinouts for the internal front-panel USB connectors, which are also used by most other motherboard makers.

Figure 4-23. Typical front-panel USB connector pinouts (image courtesy of Intel Corporation)

Some cases provide a monolithic 10-pin USB connector that mates to motherboard USB header pins that use the standard Intel layout. With such a case, connecting the front-panel USB ports is a simple matter of plugging that monolithic connector into the header pins on the motherboard. Unfortunately, some cases instead provide eight individual wires, each with a single connector. Figure 4-24 shows Robert (finally) getting all eight individual wires connected to the proper pins.

Figure 4-24. Connect the front-panel USB cables

If your motherboard and case make provision for front-panel FireWire and/or audio connectors, install them the same way, making sure that the pinouts of the connectors and cables correspond.

The next step is to reconnect the drive data cables to the motherboard interfaces, as shown in Figure 4-25 and Figure 4-26. Make sure to connect each data cable to the proper interface. See Chapters 7 and 8 for details.

Figure 4-25. Connect the Serial ATA data cable(s) to the motherboard interface(s)

Figure 4-26. Connect the ATA data cable(s) to the motherboard interface(s)

The next step is to reconnect the power connectors from the power supply to the motherboard. The Main ATX Power Connector is a 20-pin or 24-pin connector, usually located near the right front edge of the motherboard. Locate the corresponding cable coming from the power supply, verify that the cable is aligned properly with the connector, and press the cable firmly until it seats fully, as shown in Figure 4-27. The locking tab on the side of the connector should snap into place over the corresponding nub on the socket.

Figure 4-27. Connect the Main ATX Power Connector

Pentium 4 systems require more power to the motherboard than the standard ATX Main Power Connector supplies. Intel developed a supplementary connector, called the ATX12V Connector, that routes additional +12V current directly to the VRM (Voltage Regulator Module) that powers the processor. On most Pentium 4 motherboards, the ATX12V connector is located near the processor socket. The ATX12V connector is keyed. Orient the cable connector properly relative to the motherboard connector, and press the cable connector into place until the plastic tab locks, as shown in Figure 4-28.

Figure 4-28. Connect the ATX12V Power Connector

The next step is to reinstall the video adapter and/or any other expansion cards you removed. To do so, align each adapter with the corresponding motherboard slot. Make sure that any external connectors on the card bracket clear the edges of the slot. Carefully align the card with the slot and use both thumbs to press down firmly until it snaps into the slot, as shown in Figure 4-29.

Figure 4-29. Align the video adapter and press firmly to seat it

After you are certain that the video adapter is fully seated, secure it by inserting a screw through the bracket into the chassis, as shown in Figure 4-30. If the video card has an externally powered fan or requires an external power connection, make sure to connect a power cable to the video adapter before you move on to another task. Install any other expansion cards in the same manner, making sure to connect any power or data cables they require before you start another step.

Figure 4-30. Secure the video adapter bracket with a screw

At this point, the motherboard upgrade is nearly complete. Take a few minutes to double-check everything. Verify that all of the cables are connected properly and that there's nothing loose inside the case. We usually pick up the system and tilt it gently from side to side and then front to back to make sure there are no loose screws or other items that could cause a short. Use the following checklist:

• Power supply set to proper input voltage (see Chapter 16)

• No loose tools or screws (shake the case gently)

• Heatsink/fan unit properly mounted; CPU fan connected (see Chapter 5)

• Memory modules full seated and latched (see Chapter 6)

• Front-panel switch and indicator cables connected properly

• Front-panel I/O, USB, and other internal cables connected properly

• Hard drive data cable (see Chapter 7) connected to drive and motherboard

• Hard drive power cable connected

• Optical drive data cable (see Chapter 8) connected to drive and motherboard

• Optical drive power cable connected

• Optical drive audio cable(s) connected, if applicable

• Floppy drive data and power cables connected (if applicable)

• All drives secured to drive bay or chassis, as applicable

• Expansion cards fully seated and secured to the chassis

• Main ATX power cable connected

• ATX12V and/or auxiliary power cables connected (if applicable)

• Front and rear case fans installed and connected (if applicable)

• All cables dressed and tucked

Once you're certain that all is as it should be, it's time for the smoke test. Leave the cover off for now. Connect the power cable to the wall receptacle and then to the system unit. If your power supply has a separate rocker switch on the back that controls power to the power supply, turn that switch to the "1" or "on" position. Press the main power button on the front of the case, and the system should start up. Check to make sure that the power supply fan, CPU fan, and case fan are spinning. You should also hear the hard drive spin up and the happy beep that tells you the system is starting normally. At that point, everything should be working properly.

Turn off the system, disconnect the power cord, reinstall the access panels, and move the system back to its original location. Reconnect the display, keyboard, mouse, and any other external peripherals, and power the system up.