PSU +12V Question

toastman · 13th April 2005, 8:42 PM

I'm a complete PSU newbie. I've only ever used ATX 20 Pin connectors before. I just got my shiny new pc gear, and my motherboard and psu have an ATX +12V connector.

My question is:

Do I need to connect this as well as the standard atx one? Or is it instead of? Or do I not even need to touch it?
Thanks

phextwin · 13th April 2005, 8:51 PM

Connect both if you have them.

Some mobos will work without the 12v one, some wont, but they all need the 20 pin ATX plug.

looktall · 13th April 2005, 8:52 PM

are you talking about the 4 pin one?

you need to have that plugged in as well as the 20 pin atx plug.

terrabyte · 13th April 2005, 8:52 PM

Depends, some motherboard's need it to run, but if your board has the plug and your psu has it, plug it in.

Daveo · 13th April 2005, 8:57 PM

I think the one your talking about is a P4 connector, and that either powers the fans headers that come off the motherboard or the CPU voltages cause the stuff comin through the ATX 20pin plug isn't all that enough in some cases.

Most of the time you can get away with it, but its better to have it connected than not.

toastman · 13th April 2005, 9:12 PM

Cheers, I'll hook it up then

Thanks everyone.

jman1310 · 13th April 2005, 11:29 PM

wait, it's not good to plug the P4 plug and a standard 4 pin molex into a board
just plug one or the other preferably the P4 plug (it's square and has 2 yellow and 2 black wires)

one of my older mbs had both a molex and a P4 so be careful what you plug in

Daveo · 13th April 2005, 11:58 PM

Are you sure or just taking a guess?

looktall · 14th April 2005, 12:15 AM

some boards have a 4 pin molex in place of or in addition to a 4 pin ATX_12V plug.
this is purely for backwards compatibility and they shouldn't be both used at the same time.

however if you've got one of those nice new SLI PCI-E nforce boards, they have both plugs, but the 4 pin molex is actually used to give extra power to the video cards when you're running dual cards.

spludgey · 14th April 2005, 11:23 AM

Quote:

Originally Posted by jman1310

wait, it's not good to plug the P4 plug and a standard 4 pin molex into a board
just plug one or the other preferably the P4 plug (it's square and has 2 yellow and 2 black wires)

one of my older mbs had both a molex and a P4 so be careful what you plug in

Quote:

Originally Posted by looktall

some boards have a 4 pin molex in place of or in addition to a 4 pin ATX_12V plug.
this is purely for backwards compatibility and they shouldn't be both used at the same time.

Why? Both 12V and gnd are shorted inside the psu anyway, so it won't make a difference if you plug in both. Unless the mobo has an extremely stupid design and doesn't just run the two in parallel.

looktall · 14th April 2005, 7:09 PM

Quote:

Originally Posted by spludgey

Unless the mobo has an extremely stupid design and doesn't just run the two in parallel.

would you like to find out the hard way that your mobo doesn't?

it probably is quite safe to use them both, but why waste a molex if you don't need to?

Daveo · 14th April 2005, 8:16 PM

Quote:

Originally Posted by looktall

would you like to find out the hard way that your mobo doesn't?

Well yes I would, just to find out (but my motherboard doesn't take them)

13th April 2005, 8:42 PM	#1
toastman Member Join Date: Jun 2001 Location: Sydney Posts: 291	PSU +12V Question I'm a complete PSU newbie. I've only ever used ATX 20 Pin connectors before. I just got my shiny new pc gear, and my motherboard and psu have an ATX +12V connector. My question is: Do I need to connect this as well as the standard atx one? Or is it instead of? Or do I not even need to touch it? Thanks

13th April 2005, 8:52 PM	#3
looktall Working Class Hero Join Date: Sep 2001 Location: morley.wa.au Posts: 17,910	are you talking about the 4 pin one? you need to have that plugged in as well as the 20 pin atx plug. __________________ JoJoker endorses this product and/or comment.

13th April 2005, 8:57 PM	#5
Daveo Member Join Date: Sep 2003 Location: Sydney Posts: 1,683	I think the one your talking about is a P4 connector, and that either powers the fans headers that come off the motherboard or the CPU voltages cause the stuff comin through the ATX 20pin plug isn't all that enough in some cases. Most of the time you can get away with it, but its better to have it connected than not. Last edited by Daveo; 13th April 2005 at 8:59 PM.

14th April 2005, 12:15 AM	#9
looktall Working Class Hero Join Date: Sep 2001 Location: morley.wa.au Posts: 17,910	some boards have a 4 pin molex in place of or in addition to a 4 pin ATX_12V plug. this is purely for backwards compatibility and they shouldn't be both used at the same time. however if you've got one of those nice new SLI PCI-E nforce boards, they have both plugs, but the 4 pin molex is actually used to give extra power to the video cards when you're running dual cards. __________________ JoJoker endorses this product and/or comment.

13th April 2005, 8:51 PM	#2
phextwin Member Join Date: Aug 2003 Location: Geelong Velocity:Unknown Posts: 4,222	Connect both if you have them. Some mobos will work without the 12v one, some wont, but they all need the 20 pin ATX plug.

13th April 2005, 9:12 PM	#6
toastman Member Join Date: Jun 2001 Location: Sydney Posts: 291	Cheers, I'll hook it up then Thanks everyone.

13th April 2005, 11:29 PM	#7
jman1310 Member Join Date: Apr 2005 Posts: 3	wait, it's not good to plug the P4 plug and a standard 4 pin molex into a board just plug one or the other preferably the P4 plug (it's square and has 2 yellow and 2 black wires) one of my older mbs had both a molex and a P4 so be careful what you plug in

13th April 2005, 11:58 PM	#8
Daveo Member Join Date: Sep 2003 Location: Sydney Posts: 1,683	Are you sure or just taking a guess?