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Old May 26, 2013, 10:03 AM
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I have the XFX 750W black edition running my rig w/ 2x7950 and some unlisted things no problems at all. Somerhing sounds wrong, a good 750W like XFX 750W is loads for a 7950 CF
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Old May 26, 2013, 10:22 AM
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Thank you Ted for adding to my thread. That is the insight I was looking to get.
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Old May 26, 2013, 04:58 PM
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To clarify my previous post. I do think your 750w should be able to power your computer without issue (at least at stock clocks). A stock 7950 shouldn't shouldn't go more than 200w each and say 150 peak for the cpu. That's 550w plus peripherals. So stock I would say at a very high peak maybe 600w DC. At 80% efficiency that would be 720w from the wall (IMO as a highest peak...normal use would likely be no higher than 650w AC for gaming I would think). That fact you are pulling an 850w from the wall is the issue. I would not operate constantly at that load on a 750w PSU.

Out of curiosity I recommend running everything at stock clocks and voltages and load up the system (to the same as when you measured the 850w) to see what kind of power draw you get. I think either your PSU is running inefficient, or your OCed components just plain out using too much power for it.
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Old May 26, 2013, 05:46 PM
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Quote:
Originally Posted by Bond007 View Post
That fact you are pulling an 850w from the wall is the issue. I would not operate constantly at that load on a 750w PSU.
I agree completely. After my initial attempt to run both 7950 off of the XFX PSU I immediately pulled the cards. The instability was near instant.

For more info I will say that I was mining litecoins on said machine with the xfx PSU. The cpu was idle and only the two 7950 were pulling hard. They are vcore locked to 1.25v and I am not willing to run stock clocks. Currently I am sitting at a nice KH/s sweet spot and altering the clocks speeds greatly reduces the performance. I wish the vcore was not locked. That way I could lower it like I did on my 7970. I was able to reduce its AC draw by almost 100W under load!!

Back to the XFX PRO750W I think you are correct. There is something wrong with this XFX psu. It is inefficient and I have noticed that the fan speeds up prematurely. If I have the time I will swap both 7950 into another rig and monitor the AC usage.
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