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ATX power supplies

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Badar

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I had been using a simple ATX power supply with a single 12V rail of a lower wattage.But now i want to buy 500 WATTS EXTREME POWER (RP-500-PCAR) power supply which contains CPU 4+4 Pin x 1 (i take it as two 12V rails).
I can see only one 4 pin socket in my motherboard and on some other mobo's on net.Where will i connect that second 12V rail when there is no space for it on the motherboard.
I want to know for what purpose it is there and if I don't connect it with anything, will i get the full 500 watts even then.
Following is the website for further details on this power supply. **broken link removed**
 
What do you have on your motherboard that requires more +12V current than you can get from your present supply?
 
some of the newer mobos and video cards are requiring some extra 12V leads, so it's probably just overkill, and if the line is connected to a single 12V circuit then yes you're gonna get the full amps out of one plug, so the other one is just for extra hardware. Though just cause they advertise it's 500W doesn't mean you're gonna get 500W throughput on the 12V out, usually the 12V is the weakest in power compared to the 3.3/5V. On more expensive power supplies they usually give you more leads than you'll ever need, especially if you don't have any sata drives then you'll never use the sata power connectors, it's getting to the point now where molex will probably be obsolete in computers sometime soon. .
 
As far as I've seen motherboards they have a 24 pin socket where 20 pins or 24 pins cable can be inserted.there is also a a 2x2 pins socket where this 12V rail can be inserted.there are other connectors for peripherals such as sata and pata drives.But my problem is that there is not another 2x2 pins socket on any mobo i've seen so far, where second 12V rail can be inserted.Where will i connect this second 12V cable or rail.
 
I feel that the 12v1 and 12v2 can deliver the peak of power only when the other voltages -especially those responsible for contol loop are loaded appropriately loaded. foe example, even if we purchase ta supply of 500 or 2*500 and loop them, the load is shared and the output from the 12v pins wont increase unless the 3.3 or 5v ( which ever is in control loop) is loaded to the full extent of both units.
 
Badar said:
As far as I've seen motherboards they have a 24 pin socket where 20 pins or 24 pins cable can be inserted.there is also a a 2x2 pins socket where this 12V rail can be inserted.there are other connectors for peripherals such as sata and pata drives.But my problem is that there is not another 2x2 pins socket on any mobo i've seen so far, where second 12V rail can be inserted.Where will i connect this second 12V cable or rail.
As I said before - why does your mobo need more current?
Does anyone know what +12V is used for on the motherboard, besides the fans?
 
Roff said:
As I said before - why does your mobo need more current?
Does anyone know what +12V is used for on the motherboard, besides the fans?
I'm pretty sure it's regulated down anyway, but:
https://en.wikipedia.org/wiki/ATX#Power_supply
Wikipedia said:
With the introduction of the Pentium 4, the standard 20-pin ATX power connector was deemed inadequate to supply increasing electrical load requirements. The standard was revised with an extra 4-pin, 12-volt connector. This was later adopted by Athlon XP and Athlon 64 systems. Various high-end systems may have other forms of supplemental power connections.
 
Presumably, it just carries extra current.
 
Hero999 said:
Presumably, it just carries extra current.
It only carries current if something draws current. What on the motherboard, or what backplane card, draws significant current from +12V?
 
I'm pretty sure they regulate it down to 3.3v on the motherboard, from what I've heard. Provides more headway for voltage ripple?
 
theinfamousbob said:
I'm pretty sure they regulate it down to 3.3v on the motherboard, from what I've heard. Provides more headway for voltage ripple?
You may be right, but I don't think so.. I just converted an old 250W supply for bench use, and it has 3.3V at 14A coming out of it. It seems illogical to put a big switching regulator on the mobo.

EDIT: Maybe you are right. I found one article that implies that they do this because of the many different low voltages that processors are run at. If our OP wants to overclock his processor, or install a more powerful one, it would need more current from +12V. I sure wish Badar would answer this question.
 
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Roff said:
It only carries current if something draws current. What on the motherboard, or what backplane card, draws significant current from +12V?
Well i am not very sure about your questiion but i think all 8 (or even more than it) USB ports, integrated VGA, onboard LAN,Integrated sound card, on board gigabit LAN's, bluetooth, all PCI slots and other slots with DIMM's too and the other options they all require motherboard powered with a high current source.And according to my knowledge 2x2 pin connector is used for processor. In my previous Intel's D915GAV motherboard there was an extra (pata power connector) to power the PCI Express slot but now they give one extra PCI Express connector.
But i am still confused with the second 12V connector.Regardless of the fact i need it or not if I wanna use it, where I'll install it.
 
Badar, I don't know what your level of expertise is, so don't be offended. I guess my concern is that you are hoping more power supply current availability will increase your computer's performance. The point I was trying to get at is that, if your computer is working now, it won't work any faster unless you change something besides the power supply.
 
Roff said:
Badar, I don't know what your level of expertise is, so don't be offended. I guess my concern is that you are hoping more power supply current availability will increase your computer's performance. The point I was trying to get at is that, if your computer is working now, it won't work any faster unless you change something besides the power supply.
Now Roff I tell you what my problem is.I have been using power supplies that were purchased under the category of bulk and they never stated more than 350 watts.And even the supplier says that this rating is not true and it doesn't give even 250 watts.I am using intel's 630+ 3.0 GHz processor and i've read somewhere that it can consume maximum of 195 watts.My 6 USB ports are under use and i am using two hard drives with three optical drives.Sometimes hard drives begin to sound horrible and sometimes one or some of my optical drives are not detected in WIN XP with their LED's turning on and off.I assume it as the problem of low wattage power supply.The problem becomes more prominant when i attach one more hard drive (like one from my friend).
So i want to go for a genuine power supply this time with good power ratings at an affordable price.The above stated power supply suits my budget.
Now i don't want that the wattage of this power supply also falls around 250 watts if i leave 12V2 rail unconnected where i have two RAM modules with one sound card and one TVTuner card installed on my PCI slots.And i want to add some good graphics card too.
So i guess i need at least full 500 watts power supply.
 
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