What does the 12V rail power?

Dell / Optiplex gx270...
July 7, 2009 at 08:25:26
Specs: Windows XP Home Edition, Intel P4 2.8Ghz/1024Mb
I know it powers fans, hard drives, and cd/dvd
drives, but what else?

Manufacturer: Dell computer corporation
Model: Optiplex gx270
OS: Microsoft Windows XP Professional CPU/Ram: 2.793 GHz / 1022 MB
Video Card: ATI Radeon 9600 Pro (128mb)

See More: What does the 12V rail power?

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July 7, 2009 at 09:03:17
Much of the power to run the CPU comes from +12V. Some of the pins on the 20/24 pin power connector are 12V.

There is an auxiliary connector of at least 4 pins in a square configuration that plugs directly into the mother board that is also 12V.

PCIe 16 graphics cards run on 12V and many higher end cards also require an additional 12V connector to the card.

Not sure what voltage the PCI cards use.

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July 7, 2009 at 10:26:53
The major users of the +12v rail are the CPU & the video card.

Modern CPU's (Athlon, P4 & newer) get 100% of their power from the +12v rail. Prior to that, CPU's got all their power from the +5v. So if you have a high wattage CPU, 140W for instance, it will require up to 12A from the +12v.

Video cards are the other main +12v power users these days. The PCI-e x16 express slot can provide up to 75W. A 6-pin PCI-e plug can add up to 75W more, all from the +12v rail, & an 8-pin PCI-e plug can add up to 150W, also all from the +12v rail. Power requirements for video cards can vary widely depending on the make/model. There are a few high end cards that require two PCI-e plugs, so you can see how a gaming card can really put a strain on the +12v.

The following explains the voltage/wattage/amperage breakdowns of all the various plugs:


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