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Discussion Starter · #1 ·
Here is a reference for the pinouts for the various power plugs in a PC. There are numerous sources so I found the ones with the best pics and diagrams. I AM NOT RESPONSIBLE FOR ANY DAMAGES DONE USING THE FOLLOW INFORMATION.

General Wiring
These are the standard wire colors but not all manufacturers follow it. The pinouts diagrams are more reliable.
Black = Ground
Orange = +3.3v
Red = +5v
Yellow = +12v
White = -5v
Blue = -12v

Wiring VDrop Calculator
Longer and thinner wires increases Vdrop. Calculator is at the bottom of the page. Most PSUs use 18ga wires and occasionally 20ga. If you notice, these wires are rated to handle more current than what we normally provide. The reason is that as you increase the current through the wire, the more voltage-drop will be experienced.
http://www.powerstream.com/Wire_Size.htm

Motherboard
24-pin ATX, main plug on motherboards (short pin 16 to any GND to turn the PSU on)
http://pinouts.ru/Power/atx_v2_pinout.shtml

20-pin ATX, main plug on older motherboards (short pin 14 to any GND to turn the PSU on)
http://pinouts.ru/Power/atxpower_pinout.shtml

4-pin AUX, used on motherboards to power CPU
http://pinouts.ru/Power/atx12v_pinout.shtml

8-pin EPS, desktop motherboards can use just 4-pin AUX
http://www.playtool.com/pages/psucon...tors.html#eps8

Peripheral
4-pin floppy
http://pinouts.ru/Power/SmallPower_pinout.shtml

4-pin "Molex" peripheral
http://www.technick.net/public/code/...mth_power_5_25

SATA (pins 1,2,3 are not needed for desktop PCs. The 3.3v are used for delayed startup in servers)
http://pinouts.ru/Power/sata-power_pinout.shtml

3-pin Fan, sensor is optional.
http://www.interfacebus.com/ATX_Moth...or_Pinout.html

4-pin PWM fan, sensor and control are optional
http://pavouk.org/hw/fan/en_fan4wire.html

Motherboard Slots
PCI can each provide 25w at 3.3v, 25w at 5v, and 6w at 12v. However, total power is shared among all PCI slots. A motherboard maybe able only to provide a combined 100-150w to all the PCI slots.

PCI-X provides up to 25w, [more to come]

AGP provides up to 25w at 12v, [more to come]

PCI Express provides up to 75w at 12v

PCI Express 2.0 provides up to 150w (200w+ is possible) at 12v

USB, do not exceed 2.5w at 5v
http://pinouts.ws/usb-pinout.html

Firewire [IEEE1394], do not exceed 15w varying 12-25v
http://pinouts.ru/Slots/ieee1394_pinout.shtml

Video Card
6-pin PCIe, delivers 75w: three +12v, three GND

8-pin PCIe, delivers 150w: three +12v, five GND (not electrically compatible with the CPU's EPS plugs!)
 

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I needed the USB pinout for my iPod, so I could charge it directly off my PSU

Nice guide
 

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Discussion Starter · #4 ·
Quote:

Originally Posted by killnine View Post
Nice. Now what about converting my 6-pin PCIe to 8-pin PCIe with a converter?
+12v = +12v
GND = GND

In theory, the 8-pin PCIe plug can be replaced with just one +12v and one GND plug. However, the only reason that they split the plug up is to reduce wire resistence. You get much greater Vdrop and heat if you push 100w on a single long 18ga wire than 4 long 18ga wires. If your apdapter length is short and you are using thick wires, there should be no issues.
 
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thanks for this guide. I've never been in the technical side of computers, and haven't the slightest what I'm doing, but want to splice some old female molex connectors on some fans, since they only have odd connections, not the usual fan connections for motherboards.

Looking at the diagram for Molex connectors, the peripheral one is female, correct? meaning, if I have a fan with only 2 wires (Red & black), I connect the red to the yellow, (pin 1) and the black to (pin 2) Black. Yes? I know I can just try it, but why blow my stuff up, when someone probably already had the answer.

thanks again.
 

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Discussion Starter · #6 ·
Quote:

Originally Posted by lobi View Post
thanks for this guide. I've never been in the technical side of computers, and haven't the slightest what I'm doing, but want to splice some old female molex connectors on some fans, since they only have odd connections, not the usual fan connections for motherboards.

Looking at the diagram for Molex connectors, the peripheral one is female, correct? meaning, if I have a fan with only 2 wires (Red & black), I connect the red to the yellow, (pin 1) and the black to (pin 2) Black. Yes? I know I can just try it, but why blow my stuff up, when someone probably already had the answer.

thanks again.
Good idea... I'll add which plug is providing power later.
 

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Discussion Starter · #8 ·
Quote:

Originally Posted by Mootsfox View Post
I'm curious why the 8-pin pci-e gained only one 12+v line, but doubled in it's power delivery.
Probably that the vDrop is consider acceptable...

Vdrop of 75w with three 18ga copper wires over 2ft = 0.055v (a .46% drop on 12v)
Vdrop of 150w with four 18ga copper wires over 2ft = 0.082v (a .68% drop on 12v)
 

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Quote:

Originally Posted by gonX View Post
I needed the USB pinout for my iPod, so I could charge it directly off my PSU

Nice guide

Can't you just plug it in to your computer via USB or Firewire?
 

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Discussion Starter · #11 ·
Quote:

Originally Posted by Fishie36 View Post
Wow, firewire has some really bizzare specs. 45w and 30v? You could kill yourself with that, it has happened before on only 30v.
45w and up to 30v. It is variable....
 

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Quote:

Originally Posted by Muhahahaha View Post
Can't you just plug it in to your computer via USB or Firewire?
No, because I need to do it while my computer is off
I got a reserve PSU for this
 

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60W.... what are you running off that
 

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odd... I would probably use two to be on the safe side
 

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Thats what I was thinking.

The screen has a four port plug and an external power brick, but I don't have that brick. I'm guessing it's got two 12V and two grounds. It's rated at 5A, but I doubt it actually uses that much. My 22" uses about 45w, and this is a 15" screen.
 

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just to make sure I am reading this right with the 8pin pci-express plug in. it's 4 +12v wires on top and 4 gnd wires on bottom

is the plugin compatible with a 12v 8 plug EPS plugin? I could rewire to fit as long as it is.
 

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Discussion Starter · #19 ·
Quote:

Originally Posted by rx7speed View Post
just to make sure I am reading this right with the 8pin pci-express plug in. it's 4 +12v wires on top and 4 gnd wires on bottom

is the plugin compatible with a 12v 8 plug EPS plugin? I could rewire to fit as long as it is.
Correct, it is four +12v and four GND.

The plug is not compatible with the EPS plug. If you are using a multi-rail PSU, the AUX/EPS line generally gets its own rail already.
 

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just to make sure I understand is the plug not compatible as in the shape or is it the wiring? as long as it physically fits I'm happy. if the plug has a physical difference I might be albe to take another plug and cut off two pins and then bond them to the 6pin pci-e plug to get them to fit. do you know what plug that would have those two pins top and bottom that would fit in the extra 2 plugs on the 8pin plug?
 
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