P8 and P9 connector

Updated: 04/26/2017 by Computer Hope

P8 / P9 power AT style connectorAlternatively referred to as the AT style connector.  P8 connector and P9 connector as they are labeled on the motherboard and most power cables, are IBM power connectors that connect the power supply to the motherboard on AT, Baby AT and LPX motherboards. The picture to the right, is an example of this connector. With the introduction of ATX motherboards and power supplies these been replaced by the ATX style connector.

One of the most difficult and troublesome parts of this connector was the fact that both the P8 and P9 connector looked identical. Although these connections were keyed, it was still possible to put the P8 connector into the P9 port on the motherboard or visa-versa, which would physically damage the motherboard. When working with this style of connector it's important to realize that the black cables point into each other as shown in the picture below.

P8 and P9 power cables

Finally, below is the pin-out descriptions for the P8 and P9 power connectors.

Pin Color Function Connector
1 Orange "Power Good" P8
2 Red (XT No Wire) +5V DC P8
3 Yellow +12V DC P8
4 Blue -12V DC P8
5 Black Ground P8
6 Black Ground P8
7 Black Ground P9
8 Black Ground P9
9 Black Ground P9
10 Yellow -5V DC P9
11 Red +5V DC P9
12 Red +5V DC P9

Motherboard terms, Power terms