July 2003
Beginner to intermediate
874 pages
38h 13m
English
Content preview from PC Hardware in a Nutshell, 3rd Edition
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AT Main Power Connector
Table 26-11 lists the standard AT Main Power Connector pinouts used by all AT power supply variants, including Desktop/AT, Tower/AT, Desktop/BAT, Tower/BAT, and LPX. PC/XT power supplies use the same pinouts, except that Pin P8-2 is unused. In addition to supplying various standard voltages, this connector includes a special-purpose pin. Pin P8-1, PG, carries the Power Good signal, which the power supply asserts once it has started and stabilized. The motherboard will not attempt to boot until the power supply asserts PG.
Table 26-11. Standard motherboard connector pinouts for an AT power supply
|
Pin |
Color |
Signal |
Pin |
Color |
Signal | |
|---|---|---|---|---|---|---|
|
P8-1 |
orange (white) |
PG |
P9-1 |
black |
ground | |
|
P8-2 |
red |
+5V |
P9-2 |
black |
ground | |
|
P8-3 |
yellow |
+12V |
P9-3 |
white (blue) |
-5V | |
|
P8-4 |
blue (brown) |
-12V |
P9-4 |
red |
+5V | |
|
P8-5 |
black |
ground |
P9-5 |
red |
+5V | |
|
P8-6 |
black |
ground |
P9-6 |
red |
+5V |
Note that P8 and P9 are separate connectors from the power supply, but mate to a combined connector on the motherboard.
Warning
The P8 and P9 connectors are individually keyed, but it is possible to connect P8 from the power supply to the P9 connector on the motherboard and vice versa, with potentially catastrophic results.
P8 and P9 were IBM’s original designation for these connectors. Not all power supplies or motherboards label these connectors, so you may have to determine which is P8 and which is P9 by examining wire colors. The colors shown are those most commonly used, but ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.