ASROCK A55M-HVS User Manual page 27

Though this motherboard provides 24-pin ATX power connector,
it can still work if you adopt a traditional 20-pin ATX power supply.
To use the 20-pin ATX power supply, please plug your power
supply along with Pin 1 and Pin 13.
ATX 12V Power Connector
(8-pin ATX12V1)
(see p.11 No. 1)
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.11 No.16)
20-Pin ATX Power Supply Installation
Please connect an ATX 12V
5 1
power supply to this connector.
8 4
4-Pin ATX 12V Power Supply Installation
This COM1 header supports a
serial port module.
27
24
12
13
1
5 1
8 4