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2 x 7950's on a 650W PSU

Nuclear Fusion said:
I think that site was taking measurements of the whole system power consumption from the sounds of it (though it isn't exactly clear) since it shows a 3770k pulling 81w at idle at stock settings, which is higher than the 77W TDP.
Click to expand...

I woudn't disagree with that and I was just giving a max possible and still getting under your 650W. I frown on people who say "Not enough, get a bigger PSU" without doing any research or have any knowledge.

That test is 'from the wall' and I assume that they have MOBO/CPU/SSD and Heatsink fan being used.

If you are wanting to get another 7950, go for it and buy a wall meter that Tommy mentioned and let us know how much power is needed :) That way you will help others of similar situations and questions.
 
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Nuclear Fusion said:
I think that site was taking measurements of the whole system power consumption from the sounds of it (though it isn't exactly clear) since it shows a 3770k pulling 81w at idle at stock settings, which is higher than the 77W TDP.
Click to expand...

Really it is the continuous current rating of the psu that is more applicable than out and out wattage (cheapo 750 watt psu might still not cut it etc).
You have a good psu though.

You might not oc too high though if you got 2 x 7950 as the performance would be stonking anyway?
 
I would say yes a good quality 650W would be fine. (Is your XFX Seasonic built?)

I recently had a chance to play with a system with i7-3770K, a Asus 7950 (900Mhz so factory OC'ed), a Seasonic 620W, 1 HDD, 1 SSD and some case fans.

With the CPU modestly overclocked to 4.4GHz (just with the multiplier changed - voltage left at default) and with the 7950 running MSI Kompustor the most I was able to draw at the wall was 338W. And that was while really trying since I also tried the Crysis 1 GPU demo which only managed to pull 213W at the exact same settings. That Asus had an ASIC quality of 60% and defaulted to 1.07V so it was not the worst case but far from the best scenario.

TPU measured a 7950 drawing 200W at max (i.e. running FurMark) (LINK). So 2nd one even OC'ed would bring the system up to max 540W.

But HT4U.NET might be better for measuring OC draw, for instance in this review and even 1060MHz they max they measured was 186W.

Also, while the CPU was only modestly overclocked (stock voltage) the 340W was at the mains, the PSU is 80% rated so that's more like 270W. Also, 3770K != 3570K obviously.
 
Of course, a good quality 650W psu actually puts out much more. They are like 650W minimum right?

Checking the power usage at the wall is a good idea, I'll probs go to the shop and buy a power monitor myself just out of interest.
 
I use a 500W PSU for my system and it barely manages. If I try to voltage OC my card the system shuts off as if I'd pulled the plug. Would adding another 150w give enough room for another card maybe... but you probably won't be able to adjust the volts on the cards.
 
Although my system isnt quite as powerful as yours, I recently had a similar question.

I have a AMD X4 running at 3.6GHz with all 6 cores unlocked, the usual SSD&HDD/DVD Drive etc plus a ATI 6770 which is fairly thirsty for a oldish card, then I decided I wanted to go Crossfire but the problem was I only had a 500w PSU. It's a OCZ so a fairly good make, but everywhere suggested it was 650w+ for Crossfire.

Well I took the plunge and its running fine, not had any crashes. Lasted all the stress testing and hours of gameplay. I still may purchase a bigger PSU for some extra headroom when I can afford it (bring back the days of £15 PSU's being enough for most systems!)
 
How much voltage are you trying to add? If I put too much my card has overvoltage protection I think and the system just clicks off and is a pain to get going again lol.
 
Wall readings are higher than the psu's actual usage. Depends on the efficiency. My 660 ti w/ 2500k uses only 210 watts playing bf3. Same pc but with a 570 uses 250w. This is with a bequiet 650w 80+ gold.

SLI 570's ~500w but with a different psu though ( xfx 750w ). Taking efficiency into account it's closer to 430w so I'd say 650w is fine for your system.
 
I purchased a power monitor for £10. My rig with 7970 at stock and [email protected] 1.29v will use 350-390w max, 100w idle. I imagine with
the gpu overclocked it would run at 400 or so but not much more. Very comfortable for my 600w psu.
 
I also bought a power monitor.

My PC is a AMD X4 unlocked to 6 cores @ 3.6Ghz, 8GB ram @ 1800, Crossfired 6770 & 5770 plus a SDD, SATA HDD and a DVDRW. I have USB stuff plugged into it too and 3 fans etc.

Anyway the most I can get it to pull is 360w, but goes between 320-350w mostly. Idles at 160w. My 500w PSU seems comfy enough. I'm currently rendering a 1080p video and its drawing 285w with all 6 cores maxed out.
 
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