ASROCK H77M User Manual page 35

Though this motherboard provides 8-pin ATX 12V power connector, it can still work
if you adopt a traditional 4-pin ATX 12V power supply. To use the 4-pin ATX power
supply, please plug your power supply along with Pin 1 and Pin 5.
Serial port Header
(9-pin COM1)
(see p.13, No. 24)
HDMI_SPDIF Header
(2-pin HDMI_SPDIF1)
(see p.13, No. 28)
4-Pin ATX 12V Power Supply Installation
This COM1 header supports a
serial port module.
HDMI_SPDIF header, providing
1
SPDIF audio output to HDMI
GND
SPDIFOUT
VGA card, allows the system to
connect HDMI Digital TV/
projector/LCD devices. Please
connect the HDMI_SPDIF
connector of HDMI VGA card to
this header.
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5 1
8 4