Asus RS700-X7/PS4 - Manual (Page 58)

Chapter 4: Motherboard information 4-16
13. 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.