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+12V Rails?

post #1 of 11
Thread Starter 
So I have an NVIDIA GeForce GTX 550 Ti and I need a PSU to power it... I need 24A on the +12V rail, however I can not find this on any power supplies (I have a very low budget), however I have been able to find multiple ones in my price range with multiple +12V rails... so if I have 2 12V rails each with 18A, will this power my GTX 550?
post #2 of 11
They mean 24A on all +12V rails combined (and you don't sum the individual rails since it doesn't work that way; look for the combined rating on the label...if there's no combined total +12V rating, they probably have something to hide so get something else).

However, a GTX 550 Ti by itself only uses like 8A on +12V (96W) while heavily stressed, unless you overclock it. 24A on +12V is just a safe guideline, assuming you maybe have a power-hungry CPU and several hard drives.

What's everything you're going to be powering? What are your power supply options (where are you buying)? Power supplies vary widely in quality, and advertised specs on the labels don't mean that much, even if they were all true--and they're often not.
post #3 of 11
Quote:
Originally Posted by rhartnett35 View Post

So I have an NVIDIA GeForce GTX 550 Ti and I need a PSU to power it... I need 24A on the +12V rail, however I can not find this on any power supplies (I have a very low budget), however I have been able to find multiple ones in my price range with multiple +12V rails... so if I have 2 12V rails each with 18A, will this power my GTX 550?

In a word. No.

A little history:

As PSU manufacturers started to put more and more power into their products there was a concern that "the government" would get invilved (read: regulation) as it became easier and easier for computer enthusiasts to kill themselves.

So they adopted as a sort of volentary standard that they would linit the amount of power in any one "rail". The more unscrupulous manufactures (ie inexpensive PSUs) figured that if they gave people PSUs with 4 x 25 amps, no one was really going to use all four rails to the max all the time. So, they could supply a PSU advertised as 25 amps on each rail, but the PSU only had to supply a total of, say, 50 amps, since few ,if any, people need 100 amps total.

If the video card maker says you need 28 (or whatever amps) for their card, then you need that many amps.

Now, if you look at the name plate on a PSU it will list the amps it can supply to each and every rail, but if you add up all the rails (12V, 5V, 3V) you will almost always see that they add up to more that the PSU can supply. So, if it says 30 amps to a 12v rail that means that that 30 amps, PLUS what you are using from the other rails can't add up to more that the PSU can supply. And the cheaper the PSU the worse the things that will happen as to get closse to the limit of the PSU (to say nothing of what happens if you exceed it!).

The "more expensive" PSUs also have superior current controls and overload protection circuits. There's a big difference (in safety to your components and performance) between a $39.95, 300 watt PSU and a $200.00, 300 watt PSU!

Saving a few dollars on a PSU is an easy way to spend a lot of money on burned out computer parts.

Oh, and volts x amps = watts
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post #4 of 11
Quote:
Originally Posted by rhartnett35 View Post

So I have an NVIDIA GeForce GTX 550 Ti and I need a PSU to power it... I need 24A on the +12V rail, however I can not find this on any power supplies (I have a very low budget), however I have been able to find multiple ones in my price range with multiple +12V rails... so if I have 2 12V rails each with 18A, will this power my GTX 550?

No. What budget you have and what system are you running? You don't just add A up from each +12V rail. Think of rail as individual highway with speed limit, you don't just add speed limit up.
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post #5 of 11
Thread Starter 
All I have to power is a HDD, the processor (i3), and an optical drive, as well as the card obviously. My limit is $50

Would this work?
http://www.newegg.com/Product/Product.aspx?Item=N82E16817256060&nm_mc=OTC-Froogle&cm_mmc=OTC-Froogle-_-Power+Supplies-_-Silverstone-_-17256060
Edited by rhartnett35 - 12/27/11 at 6:30pm
post #6 of 11
Quote:
Originally Posted by rhartnett35 View Post

All I have to power is a HDD, the processor (i3), and an optical drive, as well as the card obviously. My limit is $50
Would this work?
http://www.newegg.com/Product/Product.aspx?Item=N82E16817256060&nm_mc=OTC-Froogle&cm_mmc=OTC-Froogle-_-Power+Supplies-_-Silverstone-_-17256060

Yes. thumb.gif
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post #7 of 11
Antec's neo eco 400w is cheaper and more powerful. The 620 version is only slightly more than the Silverstone if you include shipping.

On my atrix for this one...
Edited by qwertymac93 - 12/27/11 at 7:12pm
z87
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post #8 of 11
Thread Starter 
post #9 of 11
I really suggest this instead: www.newegg.com/Product/Product.aspx?Item=N82E16817139026
The Cooler Master GX450 isn't horrible, but for around the same price, the Corsair is significantly better.
post #10 of 11
Quote:
Originally Posted by Shub View Post

I really suggest this instead: www.newegg.com/Product/Product.aspx?Item=N82E16817139026
The Cooler Master GX450 isn't horrible, but for around the same price, the Corsair is significantly better.

Agreed with that. Corsair won't blow up on ya whatever ya do to it. It would be a very sturdy buy and will serve you well.
 
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