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PC Hardware in a Nutshell, 3rd Edition by Barbara Fritchman Thompson, Robert Bruce Thompson

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ATX Main Power Connector

Table 26-12 lists the pinouts for the ATX Main Power Connector of an ATX or ATX12V power supply. This is a 2X10 connector with Pin 1 keyed. The motherboard connector is a Molex 39-29-9202 or equivalent. The power supply connector is a Molex 39-01-2200 or equivalent. All wires are 18 AWG, except Pin 11, which is specified as 22 AWG. For power supplies 300W or larger, the specification recommends using 16 AWG wires for +3.3VDC, +5VDC, and COM (ground). Note that wire colors are those recommended and commonly used, but may vary.

Table 26-12. ATX Main Power Connector configuration

Pin

Color

Signal

Pin

Color

Signal

1

orange

+3.3VDC

11

orange

3.3VDC

2

orange

+3.3VDC

12

blue

-12VDC

3

black

COM

13

black

COM

4

red

+5VDC

14

green

PS-- ON

5

black

COM

15

black

COM

6

red

+5VDC

16

black

COM

7

black

COM

17

black

COM

8

gray

PW-- OK

18

white

-5VDC

9

purple

5VSB

19

red

5VDC

10

yellow

+12VDC

20

red

5VDC

In addition to supplying various standard voltages, this connector includes four special-purpose pins:

Pin 8 (PW_OK)

PW_OK is the ATX equivalent of the AT Power Good signal, which the power supply asserts once it has stabilized. The motherboard will not attempt to boot until the power supply asserts PW_OK.

Pin 9 (5Vsb)

5Vsb is the +5V standby circuit, which supplies +5V at low amperage to the motherboard even when the power supply is off. Any ATX power supply must provide at least 10 mA 5VSB, but motherboards ...

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