2.ATX power connectors (24-pin EATXPWR, 4-pin ATX12V)

These connectors are for an ATX power supply. The plugs from the power supply are designed to fit these connectors in only one orientation. Find the proper orientation and push down firmly until the connectors completely fit.

ATX12V EATXPWR

+12V DC +12V DC

PIN 1

GND

GND

A55BM-A/USB3

+3 Volts

+12 Volts

+12 Volts

+5V Standby

Power OK

GND

+5 Volts

GND

+5 Volts

GND

+3 Volts

+3 Volts

PIN 1

GND

+5 Volts

+5 Volts

+5 Volts

-5 Volts

GND

GND

GND

PSON#

GND

-12 Volts +3 Volts

A55BM-A/USB3 ATX power connectors

•We recommend that you use an ATX 12V Specification 2.0‑compliant power supply unit (PSU) with a minimum of 300W power rating. This PSU type has 24-pin and 4-pin power plugs.

•If you intend to use a PSU with 20-pin and 4-pin power plugs, ensure that the 20-pin power plug can provide at least 15 A on +12 V and that the PSU has a minimum power rating of 300W. The system may become unstable or may not boot up if the power is inadequate.

•DO NOT forget to connect the 4-pin ATX +12V power plug. Otherwise, the system will not boot up.

•We recommend that you use a PSU with higher power output when configuring a system with more power-consuming devices or when you intend to install additional devices. The system may become unstable or may not boot up if the power is inadequate.

•If you are uncertain about the minimum power supply requirement for your system, refer to the Recommended Power Supply Wattage Calculator at http://support.asus. com/PowerSupplyCalculator/PSCalculator.aspx?SLanguage=en-us for details.

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Chapter 1: Product introduction