Asus DSBF-DM/SAS - Manual (Page 35)

ASUS DSBF-DM Series 2-15
4. Repeat steps 1 to 3 to install the other heatsink if you have installed a second
CPU, then connect the fan cable to the 4-pin connector labeled CPU_FAN2.
2. Use a Phillips screwdriver to tighten
the four heatsink screws in a
diagonal sequence.
DO NOT forget to connect
the CPU fan cable! Hardware
monitoring errors may occur if
you fail to plug this connector.
3. Connect the fan cable to the 4-pin
connector labeled CPU_FAN1.
CPU_FAN1
connector