Asus Z9PA-U8 - Manual (Page 56)

2-36 Chapter 2: Hardware information
10. Power Supply SMBus connector (5-pin PSUSMB1)
This connector allows you to connect SMBus (System Management Bus) to
the power supply unit to read PSU information. Devices communicate with an
SMBus host and/or other SMBus devices using the SMBus interface.