Hardware Reference
In-Depth Information
The main power connector is always required, but the other two are optional depending
on the application. Consequently, a given ATX or ATX12V power supply can have up to
four combinations of connectors, as listed here:
• Main power connector only
• Main and auxiliary
• Main and +12V
• Main, auxiliary, and +12V
Themostcommonvarietiesarethoseincludingthemainonlyandthosewiththemainand
+12V connectors. Most motherboards that use the +12V connector do not use the auxili-
ary connector, and vice versa.
20-Pin Main Power Connector
The 20-pin main power connector is standard for all power supplies conforming to the
ATX and ATX12V 1.x power supply form factors and consists of a Molex Mini-Fit Jr.
connectorhousingwithfemaleterminals.Forreference,theconnectorisMolexpartnum-
ber39-01-2200(orequivalent), andthestandard terminals arepartnumber5556(see
Fig-
ure 18.20
)
. This is a 20-pin keyed connector with pins configured as shown in
Table 18.5
.
The colors for the wires listed are those the ATX standard recommends; however, to en-
able them to vary from manufacturer to manufacturer, they are not required for compli-
ance to the specification. I like to show these connector pinouts in a wire end view, which
shows how the pins are arranged looking at the back of the connector (from the wire and
nottheterminalend).Thisway,youcanseehowtheywouldbeorientedifyouwereback-
probing the connector with the connector plugged in (see
Figure 18.21
)
.
Figure 18.20
ATX 20-pin motherboard main power connector, perspective view.
