Atx 12V Power Connector; Serial Port Header - ASROCK H61M-DGS Quick Installation Manual

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

(4-pin ATX12V1)
(see p.2 No. 2)

Serial port Header

(9-pin COM1)
(see p.2 No. 17)
ASRock H61M-DGS Motherboard
20-Pin ATX Power Supply Installation
Please connect an ATX 12V
power supply to this connector.
This COM1 header supports a
serial port module.
12 24
1 13
23