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Old May 26, 2013, 12:17 AM
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Default am I expecting too much from my XFX PRO750W?

My XFX PRO 750 Watt PSU appears to be tripping the overload circuitry. I am using two 7950s and the AC draw is ~850 watts for the entire system. The PSU is ~80% efficient and so that must be factored. The XFX PRO 750 is rated for 62A DC (744Watts DC) on the 12v rail alone.

IMHO this PSU should be able to adequately power two 7950's and I am thinking there is something wrong with this PSU. I thought I would run it past the boys...

Thanks
Phill
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Old May 26, 2013, 02:23 AM
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Not an expert on PSU but if you know your system is drawing more than what the PSU is rated at, what makes you think it's the fault of the PSU when it trips / fails? It's like trying to tow 25,000 LBS of stuff with a truck that is rated 15,000 LBS and you sit there wondering why the transmission exploded.
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Old May 26, 2013, 03:07 AM
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Well, 2x7950's would only draw ~450w max on load. I doubt there's a CPU in there drawing another 400w.
Try seeing how much the PSU draws without the video cards. It's never a good thing when a PSU starts drawing more power than it's rated for.
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Old May 26, 2013, 04:21 AM
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If you are pulling that much from the wall, I would say the psu is doing exactly what I would want it to do to protect itself.

Are you running everything OC'd? Usage seems a high for a pair of hd7950 and a 3570.
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Last edited by Bond007; May 26, 2013 at 05:45 PM.
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Old May 26, 2013, 07:53 AM
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The specs for the computer are:

3570k
P8Z77-V LE PLUS
Gigabyte 7950 Windforce rev.2
2X4GB Gskill RipJaws
XFX PRO750W
Intel 520 120GB SSD
NH D-14
HAF 912

At idle the system uses ~80W AC (64W DC). Both 7950 are clocked at 1130 core and 1375 memory and thanks to gigabyte the vcore is locked at 1.25v.

From what I have read two 7950 are recommended to have no less than 45A on the 12v rail. The XFX PRO750 is rated at 62A and johnnyguru in his review thought highly of this unit.
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Old May 26, 2013, 08:06 AM
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Quote:
Originally Posted by YoungMan View Post
It's never a good thing when a PSU starts drawing more power than it's rated for.
I agree but this PSU is rated for >900W AC. Johnnyguru tested this psu hot and had no issues loading all 62A on the 12v rail. That means he drew 749.5W DC OR 900.9W AC.
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Old May 26, 2013, 08:48 AM
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Never good to run a System off a PSU so close to the "limit". Inadequate PSU creates so many problems n headaches, especially when you start OC'ing anything.

Considering the reasonable prices of a very good 850W PSU (such as Corsair), do yourself a favor, get one and ensure ample headroom above n beyond. Personally, if my Rig draws say 600W under full load fully OC'd, I would feel comfortable with 150W overhead.

Again, when looking at the price of a decent PSU vs "headaches", no brainer.
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Old May 26, 2013, 08:55 AM
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Quote:
Originally Posted by Phill View Post
The specs for the computer are:

3570k
P8Z77-V LE PLUS
Gigabyte 7950 Windforce rev.2
2X4GB Gskill RipJaws
XFX PRO750W
Intel 520 120GB SSD
NH D-14
HAF 912

At idle the system uses ~80W AC (64W DC). Both 7950 are clocked at 1130 core and 1375 memory and thanks to gigabyte the vcore is locked at 1.25v.

From what I have read two 7950 are recommended to have no less than 45A on the 12v rail. The XFX PRO750 is rated at 62A and johnnyguru in his review thought highly of this unit.
How exactly are you getting these measurements?
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Old May 26, 2013, 09:26 AM
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With my BluePlanet energy reader
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Old May 26, 2013, 09:31 AM
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Quote:
Originally Posted by rjbarker View Post
Never good to run a System off a PSU so close to the "limit". Inadequate PSU creates so many problems n headaches, especially when you start OC'ing anything.

Considering the reasonable prices of a very good 850W PSU (such as Corsair), do yourself a favor, get one and ensure ample headroom above n beyond. Personally, if my Rig draws say 600W under full load fully OC'd, I would feel comfortable with 150W overhead.

Again, when looking at the price of a decent PSU vs "headaches", no brainer.
I will not argue that. The point of my thread was to determine if my PSU is weak and therefore needs RMAing. IMO the xfx PRO750W should be able to run two 7950's without issue albeit getting close to its max. The fact that I am seeing immediate instability has me thinking there is cause to RMA it.
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