Power Supplies 101: A comprehensive guide

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? about what power supply to get

Postby earnestkm » Thu Jul 13, 2006 5:47 am

I've been out of PC building for a little bit and this article was a great start for me. I do have a question or two that I would love to get answered.

First I just purchased an HP A1540N system and a 7600GT EVGA card. The power supply that came with the system is a 300 Watt. I wasn't even going to try the card until I read this article and checked the Amps on the +12V, it was actually 18. So I tried the video card and it works. I ran Quake 4 without any problems.

Anyway my question is what Power Supply should I get? The A1540N is an X2 Processor, comes with 2 gigs of DDR2 Ram and a 250 gig SATA drive. I did take out the Modem that it comes with because I have no use for it.

http://www.shopping.hp.com/webapp/shopp ... 76AA%23ABA

There is a link to the HP website for the system.

I am going to try and move over my other DVD Burner and another HD from my old system to this new rig and I'm sure I want to get a 500 Watt Power Supply, but should I get a Dual 12V one, or triple, or even single? That was the one part that was confusing me about the article. Also my PCI Express card doesn't require a seperate power adapter to be plugged into it so I don't know if that will help.

Thanks again for this article.

Ken
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Postby jonnyGURU » Thu Jul 13, 2006 5:06 pm

Actually, 18A on the 12V is pretty good for a "mere" 300W PSU.

I best it's a decent brand like FSP or Delta, right?

If so, I wouldn't bother replacing it. Seriously.

If you do get a new one, I wouldn't worry about single vs. dual rail. Just keep in mind that for ATX12V compliance, that 12V2 is going JUST to the CPU and that everything else goes on the 12V1. So if you end up with a dual 12V rail 500W PSU with 18A on each 12V rail, the only thing your gaining is that the CPU is not on 12V2. Otherwise, you still have 18A on the 12V rail. ;)
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Postby earnestkm » Fri Jul 14, 2006 7:40 pm

Well the power supply says "HIPRO" Model is HP-D3057F3R

+5V = 25A
+12V = 19A
+3.3V = 18A
+5VSB = 2A


What's the best way to monitor the Voltages and see if it's getting what it needs? This actually is the first time I've ever really been this into finding out this stuff so please bear with me.

Thanks ahead of time

Ken
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Postby jonnyGURU » Sat Jul 15, 2006 4:56 am

Hipro is a decent brand and 19A is even better. I wouldn't worry about it.

They way to keep an eye on it is to just monitor your voltages.

Since it's the 12V in question because of the installation of the 7600GT, I'd just plug a DMM into the yellow/black of one of your Molex connectors (preferrably the same one that's feeding the aux power of your video card if your video card has one) and make sure the 12V doesn't drop too much.

Take a sample voltage idle (like sitting in the BIOS AFTER the drives spin up) and then again in Windows in a game. If the 12V rail drops more than .2V, then I would say you're probably overloading it. :D

Of course, if the 12V ever drops below 11.6V, that's not good either. ;)

EDIT: Changed .2A to .2V
Last edited by jonnyGURU on Tue Jul 18, 2006 5:29 am, edited 1 time in total.
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Postby Twisty » Mon Jul 17, 2006 5:56 am

jonnyGURU wrote:Take a sample voltage idle (like sitting in the BIOS AFTER the drives spin up) and then again in Windows in a game. If the 12V rail drops more than .2A, then I would say you're probably overloading it. :D

:!: You are the first person I have ever come across that confuses current and potential difference.
I have now left the Building :tongue8:
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Postby jonnyGURU » Tue Jul 18, 2006 5:29 am

Webster :P wrote:
jonnyGURU wrote:Take a sample voltage idle (like sitting in the BIOS AFTER the drives spin up) and then again in Windows in a game. If the 12V rail drops more than .2A, then I would say you're probably overloading it. :D

:!: You are the first person I have ever come across that confuses current and potential difference.


Darn it! I did it again!!! Didn't I!!!??

Everything I type requires three proof-readers. :(
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One more inaccuracy

Postby jumpa » Fri Jul 28, 2006 7:35 am

You state that motherboards do not use the -12V rail. This is incorrect for any motherboard that states it has PCI 2.1, 2.2 or 2.3 Compliant slots. The PCI spec requires that -12V goes to the PCI connector regardless of whether the PCI card uses it or not. This is a specification requirement and a motherboard with a PCI slot that does not have -12V connected to it is not PCI Compliant and cannot claim to be so.

There are PCI cards that do make use of the -12V although most are very old and becoming rarer by the day. It would be better to say that in a modern system no peripherals use the -12V although it is connected to PCI slots.
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Re: One more inaccuracy

Postby jonnyGURU » Fri Jul 28, 2006 10:49 am

jumpa wrote:You state that motherboards do not use the -12V rail. This is incorrect for any motherboard that states it has PCI 2.1, 2.2 or 2.3 Compliant slots. The PCI spec requires that -12V goes to the PCI connector regardless of whether the PCI card uses it or not. This is a specification requirement and a motherboard with a PCI slot that does not have -12V connected to it is not PCI Compliant and cannot claim to be so.

There are PCI cards that do make use of the -12V although most are very old and becoming rarer by the day. It would be better to say that in a modern system no peripherals use the -12V although it is connected to PCI slots.



Could you please point to where I said that. I looked and couldn't find it.

Your statement is correct. But if I said something wrong, I need to know where I said it so I know where to correct it. ;)
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Postby Doc Overclock » Fri Jul 28, 2006 2:29 pm

That would of course help yes.... :D
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Postby tedybear » Fri Jul 28, 2006 7:40 pm

http://www.hardwarebook.net/connector/bus/pci.html

It's listed as Pin-B1 I believe.

Handy page actually....

S-


(don't take it as 'gospel'...I looked up for giggles and grins the pinout of a CPU heat sink fan on the motherboard...and they screwed up at pin 3. It's not a ground...it's a sensor return feed)
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