Can my PSU handle 2 7970's?

Hey so I have one xfx 7970 with a fx-8350 and a Asus M5A99x 2.0 evo mobo. My power supply is a Corsair cx750m. I was wondering if I added another xfx 7970 in crossfire could my Psu handle it if both of them are at stock clocks? I read on another site that one guy did do it with no problems, and he said that crossfire doesn't tax your psu as much as SLI does. So i'm interested in your opinions!

 

Kevin 

I Would not risk it. An 8350 plus 2 7970's draws about 750 watts, and PSU's sometimes provide slightly less powe than they advertise.

if you have the fx 8350 at stock clocks and the 7970s at stock it will work, but you will not be able to overclock any thing as you will reach the wattage limit most likely causing your pc to shut off.

Sometimes? Always! That's what's the efficiency rating is all about. And I doubt he will geht more than 650w from the Corsair. Which means no, the PSU cannot handle 2 7970. At least nor for long.

With a strong 750W PSU, hell yes, but with that low-end, terrible voltage regulated, high-ripple, low-efficiency PSU, probably not. 750W is more than enough for two 7970s, even if your 8350 and 7970s are both overclocked. A strong, 80+ Gold unit, like a Seasonic X 750, Corsair AX750, Corsair HX750, Lepa G750, etc. are all going to handle that load perfectly fine.

No, it has nothing to do with efficiency rating. If your PSU is rated for 400w(just an example) and has efficiency around 80% at 100% load then that PSU will deliver 400w to the computer but will draw 500watt from the mains in doing so, and release the rest of that energy as heat, noise and vibration. Some quality PSU's can even deliver 110% of their rated wattage. 



But efficiency rating, bronze silver gold and platinum often are an indicator of quality. El cheapo PSU's often cannot supply their rated wattage. Here is a nice list of which ones are safe to use and probably will supply over their rated wattage: 



http://www.overclock.net/t/183810/faq-recommended-power-supplies 

As brennan already said,don't risk it with that garbage PSU. Preferably get a 700-800w from this list:  http://www.overclock.net/t/183810/faq-recommended-power-supplies

А 750W PSU will easily handle that with enough overhead for some overclocking. Don't listen to people who tell you to buy a new one.

Seriosly, people, do you ever calculate actual consumption of the system?

You are completely wrong. PSUs are branded by their output, not input power.

I do, and that's why I'm always putting 550W PSUs in single GPU systems. However, I don't use crappy PSUs in my rigs, and don't advise others do, either. The Corsair CX Builder series are low-efficiency, and are just terrible for OCing, due to terrible voltage regulation, low-end components, and low-efficiency, which is going to cost you more money in the long run. I advised a 750W PSU, but not a piece of shitzu like the CX.

This piece will to its job, especially without OC. Buying a new one at this point is a waste of money.

It's an investent in the future. The PSU is one of the few components you carry over from rig-to-rig. Buying a nice one, that is going to last longer than 2 years before blowing, is going to save you money, overall, especially if the cheap PSU blows, and takes the system with it. Just because it is Corsair does not make it quality.

Jeeeeeeez, nothing like telling a guy he has a complete piece of trash eh? You can say the same thing but a little more democratically eh?

I always advise against getting a CX series PSU; they are made cheaply, and it shows. It is a solid choice for a low-budget rig, but he has a nice computer, and it would be a shame to have it die from a PSU failure.

The CX series simply isn't an option, in my mind, when compared to other PSUs in that wattage, and roughly, in that price-range.

Yes that is true. What did I say wrong? I just corrected eppic because he implied that for example a PSU 400w rated and 80% efficiency would only supply 400*0.8 = 320 watt, which is incorrect. 

Couldn't have said it better brennan. I'm all for investing in a nice PSU.

There are many factors to consider. Use a power supply calculator like this one: http://www.extreme.outervision.com/psucalculatorlite.jsp

That will give you a clearer picture of possible full load power requirements.

Look at the post indentation to see who I replied to.

The indentation can get messy :|

 

Ow sorry, the indentation isn't clear at all.