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GPU amperage requirements

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December 27, 2012 2:08:41 AM

I just finished my first build ever and everything has been going pretty well, except that the system is not registering my graphics card. After some searching, I think it might be that the Power Supply (an Antec Basiq 550W) is not providing enough amperage off the 12V rail to my Asus Radeon HD 7870. The card says that it requires 30A off the 12V rail, while the PSU box says it delivers 25A.

I have tried plugging in two PCIe power cords off of two separate 12V rails, but that led the system to not output any display info at all, although the LEDs above the power in plugs on the Graphics Card both show as green.

Is my diagnosis of the problem correct? Do I need a new PSU? Thanks!
a b U Graphics card
December 27, 2012 2:27:18 AM

You have learned the great lesson of never buying a multi rail power supply.

Get an Antec HCG, Corsair, Silverstream or Seasonic 80+ Bronze with a SINGLE 12V RAIL.
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a b U Graphics card
December 27, 2012 12:21:42 PM

groundrat said:
You have learned the great lesson of never buying a multi rail power supply.

Get an Antec HCG, Corsair, Silverstream or Seasonic 80+ Bronze with a SINGLE 12V RAIL.

Wow, ignorance is alive and well
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a b U Graphics card
December 27, 2012 12:59:57 PM

yoda112358 said:
I just finished my first build ever and everything has been going pretty well, except that the system is not registering my graphics card. After some searching, I think it might be that the Power Supply (an Antec Basiq 550W) is not providing enough amperage off the 12V rail to my Asus Radeon HD 7870. The card says that it requires 30A off the 12V rail, while the PSU box says it delivers 25A.

I have tried plugging in two PCIe power cords off of two separate 12V rails, but that led the system to not output any display info at all, although the LEDs above the power in plugs on the Graphics Card both show as green.

Is my diagnosis of the problem correct? Do I need a new PSU? Thanks!

They reccomend a psu with 30 amps of 12v output ( or greater ) , your combined 12v output exceeds that ( on any revision of the Basiq ) , the OCP setpoint on the current revision is set for 36a
The pcie connectors are on the same rail, the modular psu connector is designed so that it can't be used in a peripheral port, so unless you used a molex to pcie adapter you weren't switching rails
Card draws some of it's power from the slot, so it's drawing from 2 of the 3 rails to begin with

PSU could be fudged
Card could be fudged
Could be something else altogether
Don't know, but the psu ( if not faulty ) can provide the power the card needs and the number of rails doesn't matter
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December 27, 2012 3:35:50 PM

So if the gpu has space on it for what looks like two six-pin PCIe power connectors, do I need to be using both, or just one?
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a b U Graphics card
December 27, 2012 3:39:33 PM

yoda112358 said:
So if the gpu has space on it for what looks like two six-pin PCIe power connectors, do I need to be using both, or just one?

Yes
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January 3, 2013 2:05:44 AM

Best answer selected by yoda112358.
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