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How can I tell which 12volt rail is being used?

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August 5, 2010 9:03:06 PM

My Question:

How can I tell which 12 volt rail is being used? And how can I tell if I'm using all 4 rails. See my specs below.

My PSU specs:

Antec TruePower New TP-750

+12V Rails: 4
Output: +3.3V@25A, +5V@25A, +12V1@25A, +12V2@25A, +12V3@25A, +12V4@25A, -12V@0.8A, +5VSB@3.0A

newegg link here:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


My system specs:

Asus M4A79XTD EVO (Crossfire ready, no SLI)
AMD Phenom II x4 955 BE 3.2Ghz
G Skill DDR3 1600 8GB
2x EVGA nVidia 9800 gtx+ (not in sli)
Antec TP 750watts
Windows 7 Pro x64
Antec 300 (5x120mm Fans + 1x 140mm Fan + 2 blue cathode lights)
Sony Dvd burner
2.5" Card Reader/Writer
Zalman 6 Fan Controller
1TB Western Digital Caviar Black
500GB Western Digital Caviar Black

Monitors:

Samsung XL2370
Dell S2009W
Cintiq 18SX

More about : 12volt rail

a c 113 B Homebuilt system
August 5, 2010 9:18:37 PM

See the table at the bottom of this page:
http://www.jonnyguru.com/modules.php?name=NDReviews&op=...

The short answer would be that each pair of 6+2 and 6-pin cables are on their own rail... so one hardwired 6+2-pin and one modular 6-pin per rail.

How do you tell the two hardwired cables apart? I can't imagine unless they are labeled.
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Best solution

a b B Homebuilt system
August 5, 2010 9:20:18 PM

At the bottom of the first page of its jonnyguru review Okalahoma Wolf marked which connectors went with which rails.
http://www.jonnyguru.com/modules.php?name=NDReviews&op=...

The connectors are split up well enough that you wont really need to worry about manually balancing your loads too much. If you use the hardwired cables then you will automatically be split pretty evenly between the rails.

Edit: Proximon beat me to it
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August 5, 2010 9:28:37 PM

Proximon said:
See the table at the bottom of this page:
http://www.jonnyguru.com/modules.php?name=NDReviews&op=...

The short answer would be that each pair of 6+2 and 6-pin cables are on their own rail... so one hardwired 6+2-pin and one modular 6-pin per rail.

How do you tell the two hardwired cables apart? I can't imagine unless they are labeled.

I am reading up on it at the moment. Will respond in a bit.
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August 5, 2010 10:06:09 PM

@Proximon and hunter315,

wow thanks guys for the link, that review was pretty easy to follow and digest. I loved how the 12volt rails were labeled. Reason why i asked this question was that I got another evga 9800 gtx+ and wasn't sure if I was getting enough amps on them. There was no way to tell for me if they are getting their own 12volt rail @25 amps.
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a b B Homebuilt system
August 5, 2010 10:09:40 PM

The power requirements listed for the card are always for the system as a whole, a 9800GTX+ only uses about 150W under full load or about 12.5A, each rail could provide enough power to handle 2 of them, you have plenty of power available to you, thats one of the upsides to a good power supply.
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August 5, 2010 10:19:47 PM

Another question comes to mind....since we're in the amps and watts topic....My question is my 9800gtx+ System Requirements on newegg says:

Minimum of a 450 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 24 Amp Amps.)
Minimum 550 Watt for SLI mode system.
(Minimum recommended power supply with +12 Volt current rating of 30 Amp Amps.)

but is it talking about the total amps of the psu on +12 volt? or is it talking about 25amps on one rail?

I read in some review or forum that 9800gtx+ at max load eats 180something watts so; 180watts divided by 12volt = 15amps .....so basically it only eats 15amps @max load and my psu 12v1, 12v2, 12v3, 12v4 are all supplied with 25 amps per rail. Did that make sense? °_·
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August 5, 2010 10:23:12 PM

hunter315 said:
The power requirements listed for the card are always for the system as a whole, a 9800GTX+ only uses about 150W under full load or about 12.5A, each rail could provide enough power to handle 2 of them, you have plenty of power available to you, thats one of the upsides to a good power supply.

lol you answered my question even before i asked it. Well thanks alot for the help. It's such a relief knowing everything is stable now that i got my 2nd graphics card installed.
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a b B Homebuilt system
August 5, 2010 10:31:25 PM

Its a pretty common question so i figured you had it too. Since the GPU pulls 75W from the slot(6.25A) which is powered by the 24 pin main, and a 6 pin provides 75W and an 8 pin provides 150W(12.5A), so in your case half the cards power comes from 12V1 and the other half comes from 12V3 or 12V4
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August 5, 2010 10:35:16 PM

Stupid question, what is a rail? Is it just a wire coming from PSU? Thanks.
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August 5, 2010 10:43:34 PM

Best answer selected by monkey_d.
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a c 113 B Homebuilt system
August 5, 2010 11:05:26 PM

orestesdd said:
Stupid question, what is a rail? Is it just a wire coming from PSU? Thanks.



Have a look at the PSU guide linked in my sig. In that you will find a link to a glossary.
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