Asus RS520-X5/PS8 - Manual (Page 54)

4-12 Chapter 4: Motherboard information
9. CPU and system fan connectors (4-pin CPU_FAN1/2, REAR_FAN1/2,
FRNT_FAN1/2/3/4, FBD_FAN1)
The fan connectors support cooling fans of 350 mA ~ 740 mA (8.88 W max.) or
a total of 3.15 A ~ 6.66 A (53.28 W max.) at +12V. Connect the fan cables to
the fan connectors on the motherboard, ensuring that the black wire of each
cable matches the ground pin of the connector.
DO NOT forget to connect the fan cables to the fan connectors. Insufficient air
flow inside the system may damage the motherboard components. These are
not jumpers! DO NOT place jumper caps on the fan connectors!
10. Power supply SMBus connector (5-pin PSUSMB1)
This connector is for the power supply SMB cable, if your power supply
supports the SMBus function.