Power Supplies - Upgrading and Repairing PCs - page 1107

Four-Pin +12V CPU Power Connector
To augment the supply of +12V power to the motherboard, Intel created a new ATX12V
power supply specification. This added a third power connector, called the +12V con-
nector , specifically to supply additional +12V power to the board. The 4-pin +12V power
connector is specified for all power supplies conforming to the ATX12V form factor and
consists of a Molex Mini-Fit Jr. connector housing with female terminals. For reference,
the connector is Molex part number 39-01-2040, and the terminals are part number 5556.
This is the same style of connector as the ATX Main power connector, except with fewer
pins.
Thisconnectorhastwo+12Vpowerpins,eachratedfor8Atotalusingstandardterminals
(or up to 11A each using HCS terminals). This allows for up to 16A or more of additional
+12V current to the motherboard, for a total of 22A of +12V when combined with the
20-pin main connector. The 4-pin +12V connector is shown in Figure 18.24 .
Figure 18.24 +12V 4-pin CPU power connector, side and terminal end view.
The pinout of the +12V power connector is shown in Table 18.14 .
Table 18.14 +12V 4-Pin CPU Power Connector Pinout (Wire End View)
Using standard terminals, each pin in the +12V connector is rated to handle up to 8 amps
of current, 11 amps with HCS terminals, or up to 12 amps with Plus HCS terminals. Even
though it uses the same design and the same terminals as the main power connector, the
current rating per terminal is higher on this 4-pin connector than on the 20-pin main be-
cause there are fewer terminals overall. By counting the number of terminals for each
voltage level, you can calculate the power-handling capability of the connector, as shown
in Table 18.15 .
Table 18.15 Maximum Power-Handling Capabilities of the 4-Pin +12V Power Connector