ASROCK Rack C2750D4I User Manual page 28

Though this motherboard provides a 4-Pin CPU fan (Quiet Fan)
connector, 3-Pin CPU fans can still work successfully even with-
out the fan speed control function. If you plan to connect a 3-Pin
CPU fan to the CPU fan connector on this motherboard, please
connect it to Pin 1-3.
ATX Power Connector
(24-pin ATXPWR1)
(see p.13 or 15, No. 1)
Though this motherboard provides a 24-pin ATX power connector,
it can still work if you adopt a traditional 20-pin ATX power supply.
To use a 20-pin ATX power supply, please plug your power supply
along Pin 1 and Pin 13.
Intelligent Platform
Management Bus header
(4-pin IPMB_1)
(see p.13 or 15, No. 24)
Non Maskable Interrupt
Button Header
(2-pin NMI_BTN1)
(see p.13 or 15, No. 21)
1 12
13 24
20-Pin ATX Power Supply Installation
IPMB_SCL
IPMB_SDA
GND
No connect
POWER
1
CONTROL
28
Pin 1-3 Connected
3-Pin Fan Installation
Please connect an ATX pow-
er supply to this connector.
1
13
This 4-pin connector is used
to provide a cabled base-
board or front panel connec-
tion for value added features
and 3rd-party add-in cards,
such as Emergency Man-
agement cards, that provide
management features using
the IPMB.
Please connect a NMI de-
vice to this header.
12
24