P8 and P9 connector

Updated: 11/16/2019 by Computer Hope
P8 / P9 power AT style connector

Alternatively referred to as the AT style connector, P8 connector, and P9 connector, the P8 and P9 are IBM power connectors. They connect the power supply to the motherboard on AT, Baby AT and LPX motherboards. The picture is an example of this connector. With the introduction of ATX, motherboards and power supplies were 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, these were 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. Doing so would physically damage the motherboard. When working with this type of connector, make sure the black cables point into each other, as shown in the picture below.

P8 and P9 power cables

Finally, below is the pinout descriptions for the P8 and P9 power connectors.

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

Motherboard terms, Power terms