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Question about Dual 12v Rails and Graphics Card 12v power requirements


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#1 bsk8r

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Posted 27 November 2012 - 05:16 AM

Ok so I'm needing to upgrade my graphics card and currently I'm stuck with a 450w BFG PSU which has 2 12v rails with 18A on each. While looking for cards I was aware of the need to make sure that the 12v rails will give off enough power, but the dual rails on my PSU has left me confused, some clarification would help. If the PSU has 2 12v rails @ 18A does that mean I can still support a graphics card that requires more than 18A? Or how exactly does that work. And if possible, what is the best graphics card I could get with this PSU, regardless of price.

PSU: http://www.newegg.com/Product/Product.aspx?Item=N82E16817702019

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#2 dpunisher

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Posted 27 November 2012 - 11:07 AM

More questions than answers really.

Can't find the specs/reviews on that particular PSU so I don't know who makes it, or if it really has 2 rails, or is just labeled as having two rails. Also, many OEMs rate each rail as 18 amps, and then combined rail amperage as 30 amps or lower. The other rails (+3.3V@22A, +5V@15A) make me wonder.

Don't know what video card you are looking at, or whether the power recommendations are just for the card, or the whole system (as many makers use).

If you do have a 450 watt supply, trying to run a 200+ watt card from it would not be a good thing.

I am a retired Ford tech. Next to Fords, any computer is a piece of cake. (The cake, its not a lie)

3770K @4.5, Corsair H100, GTX780, 16gig Samsung, Obsidian 700 (yes there is a 700)


#3 bsk8r

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Posted 27 November 2012 - 03:00 PM

Well for the PSU I had a page directly from the BFG website that listed all the specs and information about it, but their website seems to be down ATM.

As for the video card, I currently have a GT 220 and I'm looking at getting something along the lines of a 7750/7770 or GTX 550 Ti, or anything around that range, as long as my PSU is capable of supporting it, that's what I'm wondering. I was confused if the so said 2 12v rails @ 18A meant it can handle more than 18A or only up to 18A.

#4 killerx525

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Posted 27 November 2012 - 11:20 PM

Your 450W power supply should be able to power the 77xx cards easily.

>Michael 
System1: CPU- Intel Core i7-5820K @ 4.4GHz, CPU Cooler- Noctua NH-D14, RAM- G.Skill Ripjaws 16GB Kit(4Gx4) DDR3 2133MHz, SSD/HDD- Samsung 850 EVO 250GB/Western Digital Caviar Black 1TB/Seagate Barracuada 3TB, GPU- 2x EVGA GTX980 Superclocked @1360/MHz1900MHz, Motherboard- Asus X99 Deluxe, Case- Custom Mac G5, PSU- EVGA P2-1000W, Soundcard- Realtek High Definition Audio, OS- Windows 10 Pro 64-Bit
Games: APB: Reloaded, Hours played: 3100+  System2: Late 2011 Macbook Pro 15inch   OFw63FY.png


#5 szvwxcszxc

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Posted 29 November 2012 - 07:35 PM

I don't know where these people are getting their information, but you need at least a 600W power supply to run any significant graphics card. Ideally you should have 750W or more.
450W is not sufficient for even one dedicated graphics card.

Edited by szvwxcszxc, 29 November 2012 - 07:35 PM.


#6 dpunisher

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Posted 29 November 2012 - 10:10 PM

I don't know where these people are getting their information, but you need at least a 600W power supply to run any significant graphics card. Ideally you should have 750W or more.
450W is not sufficient for even one dedicated graphics card.


Not too difficult to look up. 7770 pulls 85 watts for a reference card maxxed out. Lets be generous and say 100 watts for a non reference or overclocked board. A decent 450 watt PSU (which that BFG is) will work fine for that card. Hard, really hard, to build a home system with a 77XX card that would pull even 300 watts.

I am a retired Ford tech. Next to Fords, any computer is a piece of cake. (The cake, its not a lie)

3770K @4.5, Corsair H100, GTX780, 16gig Samsung, Obsidian 700 (yes there is a 700)


#7 killerx525

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Posted 29 November 2012 - 10:11 PM

The 77xx barely draws any power and 750w for a single card is generally a overkill. 750W is mostly used in multi-gpu system. According to HardOCP, the total power draw is 222W which a 450W would be fine.

>Michael 
System1: CPU- Intel Core i7-5820K @ 4.4GHz, CPU Cooler- Noctua NH-D14, RAM- G.Skill Ripjaws 16GB Kit(4Gx4) DDR3 2133MHz, SSD/HDD- Samsung 850 EVO 250GB/Western Digital Caviar Black 1TB/Seagate Barracuada 3TB, GPU- 2x EVGA GTX980 Superclocked @1360/MHz1900MHz, Motherboard- Asus X99 Deluxe, Case- Custom Mac G5, PSU- EVGA P2-1000W, Soundcard- Realtek High Definition Audio, OS- Windows 10 Pro 64-Bit
Games: APB: Reloaded, Hours played: 3100+  System2: Late 2011 Macbook Pro 15inch   OFw63FY.png





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