A question about Graphics cards and their PSU "requirements"..

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IntegratedGraphics

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May 30, 2012
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If I buy a 7950 for my build with an i5 3470 (non OC of course), 8gb of ram and 2 hard drives, my build will realistically have an extreme load power use of say 380 watts... If I buy a 400W or 430W power supply, would I still be able to use my 7950? The 7950 says it "requires" 550W, but does that mean that if the computer detects you have a 7950, you won't even be able to use the gpu?? I'm not sure if it's actually a requirement, or merely a suggestion. Getting a 600W PSU seems really overkill for build and getting a 430 watt seasonic or a 400W rosewill fortress would save me quite a bit of money.

TLDR; 1) If I get a 7950 coupled with an i5-3470, 2 hard drives and 8gb of ram and OC my 7950 say... 20%, would it use up more than 400W?
2) Is the 550W requirement for the 7950 actually a requirement or is it possible to say... run a 7950 on a 500W PSU?

I know this may be a very stupid question, but I haven't found any resources to answer my 2nd question. Thanks for all the help.
 
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IntegratedGraphics

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But is there actually a requirement? I want to know If I can actually use a 7950 with a 450W or 500W as opposed to being forced to use a 550W
 
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jaguarskx

jaguarskx

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The issue is not how many watts the PSU is rated for but how many amps it can deliver on the +12v rails which are the most important rails since all the power hungry devices draws power from the +12v rails.

I don't really have time to check how much power the Radeon HD 7950 draws, but I think is about 175w. That works out to almost 15 amps (175w / 12v). Your CPU also draw power from the +12v rails and if you have an AMD CPU, then it is a lot more power hungry than an Intel CPU. So if you have an AMD CPU then technically you need a more powerful PSU and if you were to have an Intel CPU. Other things that draws power from the +12v rails are the fans and hard drive / optical drive motors.

Would I run a Radeon HD 7950 and an Intel Core i5 CPU on a high quality Seasonic (basically the premiere PSU manufacturer) 380w PSU? Hell no!!! A 430w PSU? Only if I had to, and only until I quickly buy and receive a 500w PSU.

If you are going to OC, then I generally recommend a 550w PSU. I think a good quality 500w PSU should be able to handle an OC'ed Radeon HD 7950, but the more the PSU is stress, the shorter it's life span.

Brand names that I recommend other than Seasonic are Corsair, XFX, Enermax, PC Power & Cooling.
 
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scout_03

scout_03

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this for the card http://www.amd.com/us/products/desktop/graphics/7000/7950/Pages/radeon-7950.aspx#2 need a nimimum 500 watts and 2 pci-e cables and to that you have to had all the other components so i would not go below 600 watts and at lest 40 amp on the 12 volts for a single line and if you want to overclock or add anoother hd7950 to you system to with a 7750 watts with 4 pci-e connector and 50 amp on the 12 volts line .
 
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Airm3n-1292454

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I personally stick around 600w psu's or higher nowadays for most system builds. You can find some good deals on 600w's heck I picked up a few ocz modstream series a little while back for about 20$ CDN a piece after rebate. Decent thing that would be good for any build aside from sli or crossfire. Corsair is usually the brand i prefer as i've never had one die on me yet.
 
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Cons29

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Feb 10, 2010
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personally i wouldn't push it, i am not comfortable knowing that the psu is at the edge of capacity already. and if you factor in capacitor aging, how much would that be 2-3 years down the line if you are at say 90% capacity at the beginning?

a good 550w should be the minimum nowadays, but that is just me. and based on reviews, psu's have their efficiency at the highest when at 50% load.
if you have a 380w rig with a 400w psu, what will happen if you oc and/or upgrade in the near future?
 
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ko888

ko888

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For a system using a single AMD reference design Radeon HD 7950 graphics card AMD specifies a minimum of a 500 Watt or greater system power supply. The power supply should also have a maximum combined +12 Volt continuous current rating of 30 Amps or greater and have at least two 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most critical factor.

Overclocking of the CPU and/or GPU(s) will require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.

The Seasonic G Series G-450 (SSR-450RM Active PFC F3), with its maximum combined +12 Volt continuous current rating of 37 Amps and with two (6+2)-pin PCI Express supplementary power connectors, is sufficient to power your system configuration with a single AMD reference design Radeon HD 7950 graphics card.

The Seasonic S12II-430 Bronze is right on the edge as long as you're not planning on running FurMark or overclocking. It can deliver more than its labelled power but that doesn't mean you should count on it.

I don't ever remember seeing a 400 Watt Rosewill Fortress but there is a 450 Watt Fortress model that would work fine.
 
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