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Minimum power requirement + volts/amps?

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March 24, 2012 7:56:53 PM

Hey guys, I have a question as I'm not too familiar with power supplies or the specifics of electrical specifications.

I will be Crossfiring two 6950's in the near future, along with my current build:

Gigabyte GA-990FXA-UD3 motherboard
AMD Phenom II X6 1055T OC @ 3.9 GHz
Mushkin Enhanced Silverline Stiletto 2x4=8GB 1333MHz RAM
Gigabyte GV-R695OC-1GD 1GB Radeon 6950
Corsair H80 Liquid Cooling System
1 Crucial M4 64GB SSD
1 WD 320 GB 7200 RPM HDD
1 Toshiba 1TB 7200 RPM HDD
8x optical drive
3 additional 120mm case fans

Currently I have no issues with my Xion 700W power supply, but I was wondering what my minimum (bare minimum under full load, so to be safe I'd add 50 watts on top) power requirements are, along with amps/voltage? I am not keen on the specifics of these things and wondered if there are any additional power supply considerations I'd need to take in order to run Crossfired 6950s?

Thanks!
March 24, 2012 8:22:49 PM

For about 20 bucks, you can purchase a Kill-A-Watt to measure your power draw.
Read the LCD display, add 20-30 watts for safety and go from there.
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Best solution

a c 1173 ) Power supply
March 24, 2012 8:36:58 PM

For a system using two Radeon HD 6950 graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 700 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 48 Amps or greater and have at least four 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important factor.

Overclocking of the CPU and/or GPU(s) will require an additional increase to the combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The extra amount of amperage required will depend on the magnitude of the overclocks you are trying to achieve.
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March 24, 2012 9:22:02 PM

watts =


voltage (v) times current (amps)

if my graphics card draws 20amps on the 12v rail

12 * 20 = 240watts
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March 25, 2012 1:31:12 AM

ko888 said:
For a system using two Radeon HD 6950 graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 700 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 48 Amps or greater and have at least four 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important factor.

Overclocking of the CPU and/or GPU(s) will require an additional increase to the combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The extra amount of amperage required will depend on the magnitude of the overclocks you are trying to achieve.


I will not be overclocking my GPUs although they are factory overclocked (800 to 870), are you pertinent to whether or not I would need additional amperage/voltage/wattage? Is your recommendation based on a 800mhz 6950 or is this irrelevant?

Thank you!

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a c 1173 ) Power supply
March 25, 2012 4:52:21 AM

alekskg said:
I will not be overclocking my GPUs although they are factory overclocked (800 to 870), are you pertinent to whether or not I would need additional amperage/voltage/wattage? Is your recommendation based on a 800mhz 6950 or is this irrelevant?

Thank you!

My numbers are based on a PowerColor HD 6950 PCS++ 2 GB @ 880 MHz Core Clock when running FurMark.

If you never run GPU stress testing utilities like FurMark or OCCT GPU:3D or similar utility then you can get away with a combined +12 Volt continuous current rating of 43 Amps or greater.

I know there's at least five 700 Watt AXP/XION models but you never specified which specific model you have.

There are some 700 Watt models that are insufficient or too close to borderline sufficiency to even power a system with two Radeon HD 6950 in 2-way CrossFireX mode.
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March 25, 2012 6:09:05 AM

You could probably handle that system on a Coolermaster silent pro gold 600w, XFX Core Edition Pro/XXX 650w, Seasonic X series 660w or the TX/HX/AX series from Corsair or HCG/TCP/HCP from Antec.

In short a good quality 600+w PSU is worth the price you pay.
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March 25, 2012 3:02:46 PM

Gentlemen, Ladies,
A dual Xeon, 48GB GTX (single)470 2 Corsair water cooled fans several hard drives, etc, barely dents a 1000 watt supply, topping out at around 600 watts while running all 24 cores overclocked BTW. It is possible that the person in question may need 2 supplies. Only he can tell, and a Kill-A-Watt is still his best bet.
Of course, if he were a tech, he might put a low ohm, high watt resistor in series with his rails and measure across them with a scope to see the peaks, but that is overkill.
Borrow or buy the Kill-A-Watt, measure first, pick a good (1200watt) supply...after all, if you're an addict as we are, you will be upgrading again soon.
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March 25, 2012 4:15:48 PM

Best answer selected by alekskg.
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March 25, 2012 4:20:20 PM

DelroyMonjo, that is my power supply. I've always been a little wary of it, not only because its a lesser known brand, but the build quality and box art just seems too crappy to take their products a little seriously, as if its second rate.

My computer was a prebuilt iBuypower system, and I'm sure they cheaped out on the PSU in the build. Since then I've replaced most of my parts except the PSU/CPU and CD/HDD. I've been checking out the CoolerMaster Silent Pro Gold and have decided I'll be grabbing an 800W with a 65 continuous amperage, just in case pcfxr4u is correct in stating that I'll be doing an upgrade soon :p .

http://www.newegg.ca/Product/Product.aspx?Item=N82E1681...

$139.99 at a local retailer (on sale)

Well, I should probably consult with my wallet first.

Thanks guys, you've been a great help.
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