Power Supply ? - Amperage / Rail

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BassAddict

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1. This is the power supply that I have, Antec CP-850: http://www.antec.com/Believe_it/product.php?id=NzIw.

First Question: It has 4 12 volt rails with two of them at 22A and the other two are rated at 25A with all rails ±5%. If all of the Amps are converted to Wattage, then it comes out to 1128 Watts. Now at the lowest (-5%) on all the amps, it comes out to 1071.6 Watts. Is the company practically saying that the Amps listed are the absolute maximum power the power supply can handle with Wattage?

Second Question: If a video card requires 42 Amps on a single rail (for ex: a GTX 580), would it be sufficient to combine two rails to power a 42 Amp video card that recommends 42 Amps on a single rail? The reason I ask, is because, the gaming series Antec PSU's max Amp on a rail is 40A. I am only experienced with Antec Power Supplies and BFG (what use to be) power supplies. So, I don't know what kind of power other companies are loading into their PSU's.

Thanks for any help / input!
 
If the wattage and amperage ratings differ, use the lowest one to be safe.

Do not go by "recommended" PSU values - they are for an entire system with that card, not the card itself. Find the TDP of that card, it will be in watts. Divide by 12 to get actual amperage at 100% load.
 
No, it does not mean they are over rating it. What it means is that each rail can have that number of amps max before it is overloaded. You do not simply add the rails together.

If you look on the label you will find that it will tell you the combined 12V rail wattage.:

DSCF0741.JPG


you have a total of 768W on the 12V rail, or 64A.

Your GTX 580 has a max power draw of 244W, or 20.333* A, which is plenty.

Even if the max on each rail was 20A, not all of the PCIe will be off the same 12V rail (not with that many), so you could distribute the load over more than one rail, and it would be safe
 
^^^ like said, your fine. Plus what Aastii said you dont add the rails together, unless its a true dual/quad rail. Which this is not. Its just the max any one rail can pull with out tripping.
 
Antec states it's a multi-rail. I couldn't find anything hinting for or against in the jonnyguru review of this unit either.

Its just the max any one rail can pull with out tripping
Click to expand...

But like you said, not if it's not a multi rail.

I doubt it really matters as the PCI-E connectors are on individual plugs. If it is a multi rail, you'll be using two rails, if it's not, it doesn't matter.
 
linkin said:
Antec states it's a multi-rail. I couldn't find anything hinting for or against in the jonnyguru review of this unit either.



But like you said, not if it's not a multi rail.

I doubt it really matters as the PCI-E connectors are on individual plugs. If it is a multi rail, you'll be using two rails, if it's not, it doesn't matter.
Click to expand...

Its a multi rail. But not a true one. Its really a single rail, with four rails fed off the single rail. With a amp. limit on each one.

This is a true multi rail. And its capable of pulling 40 amps on both rails at the same time.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139007
http://www.hardwarecanucks.com/foru...51-corsair-hx1000w-power-supply-review-8.html
 
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I have another question about the rails, but I didn't want to start a new thread for it. So, here it is:

If a card requires 45A on a single 12V rail, but the PSU has two 12V rails with 40A, could you plug one PCI pin (aka 6 pin or 6+2 pin) from one 12V rail, and then use the other PCI pin from the second 12V rail? (using a 6 or 6+2 pin from the other 12V rail)

TLDR: Instead of, using two Pins from the same Rail, can you connect two different pins from two different rails? Or, wouldn't it work that way?
 
Dont know how to really answer that since no card pulls 45 amps.

(Most) dual rails have one rail dedicated to the CPU, so everthing else pulls off the other rail. So it would not matter which connector you use, they are all on the same rail. And on like quad rail, most of the time one PCIe connector is on one rail the other is off another rail.

Your best bet is to forget about multi rails. Get a good quality single rail
 
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