3.5 Installing the Motherboard
3.5.3 Connecting power supply cables to the motherboard
After successfully installing the motherboard in the computer case, proceed with attaching the appropriate power supply connector(s) to it. This process is easy with an ATX (boards and power supply) because there is only one connector that is also keyed to fit only one way. Take more care with the older AT systems because there are two separate, but physically identical connectors that must be plugged in a specific way. This is covered in the next section.

The following are the steps for connecting the power supply cables to the motherboard:

Step 1 On an AT system, first locate the two large wire leads from the power supply labeled P8 and P9.
Step 2 Locate the large 12-pin power connector on the motherboard. It is usually found right behind the keyboard connector.
Step 3 Plug the P8 and P9 wire lead connectors in the 12-pin power connector.

Caution: Make sure the black wires are in the middle, right next to each other. If this configuration is reversed, the motherboard is likely to be damaged when the power is turned on. Pressure might have to be applied to insert the connectors. On an ATX system, there is one large 20-pin (P1) connector. It is keyed for easy installation.

Sometimes it is helpful to delay attaching the power connector to the board until all the components have been installed that need to go on the motherboard so that there will be more maneuvering room to work inside the case.

Lab Activity  (PDF, 12 KB)
  In this lab, you will place the motherboard into the case and secure it.
    
Video  (1:59 min)
  Preparing and Installing the Motherboard