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Hi All,
This may be a strange question but I wanted to clarify before I overload any power supplies. Does anyone use a R9 280X and if so do you have power consumption figures? I’m planning to use a bog standard ATX psu to run the boards and drives etc, but want to ideally use modified dell server PSU’s to provide the power to the cards.
I figure I can have 6 server psu’s in the bottom of the rig which each give 700w, I can run the 12v/Gnd from each of these up to the rig with heavy duty cable and then distribute it evenly between 12 cards.
My big question is: If I have 2 x 8 pin pci-e connectors coming from an external power source, will the cards still try to draw from the motherboard? Likewise should I modify the riser cables to take their power from this source?
The cost savings are potentially huge, 2 rigs and 12 cards is potentially around 4.2kw just for the gpus, which is going to mean 4 x 1250w supplies in total ( around £800, whereas with the server psus the total cost of power supplies goes down to £158!!)
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the 280X should pull ~280W each.
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Hmmm not as much to save as I hoped then, I may just go with dual 850w to start with, and build custom supplies as the rig expands. For some reason I thought they would be pulling closer to 390w each :-\
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with undervolting to 1.03 to 1.07 i got 180-200W (edit: this is wrong, do the math from my 4 GPU rig numbers)
these are my figures, measured at AC output, so actual DC figures are at least 8% less, or more on cheaper PSUs.
4 GPU rig 1000-1050W on AC side, seasonic 1250W
3 GPU rig - I forgot, but I run it on Enermax 860W. Find my post where I listed it on this forum
2 GPU rig - 450-500W corsair CX750mobo+cpu+ram+disk with no GPUs - around 80W.
Undervolting saves a lot of power, and heat, Full voltage at default value wears GPU fans, clogs them with dust faster. Undervolting is absolutely a must, and it’s unreasonable to run the cards at full voltage. It took me a few restarts /gpu crashes to get the optimum voltage, so it’s pretty easy. The difference in temperatures is huge too. I think mine would run at 95*C and throttling haven’t I changed the thermal paste to Gelid GC extreme and undervolted. It’s a whole different world now.
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disregard this post, I mistakenly quoted my previous post instead of editing numbers
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I currently have 3 MSI R9 280x using a 1200W Gold PSU. I have ordered a 4th 280x. With little tech experience, I am just running everything default up to this point, happy and stable. Will my current PSU handle all 4 cards? I saw a rig building spec online that was showing a 6 GPU system using a 1300W PSU- so I figured I should be fine using that math. But now after reviewing this thread, I am not so sure! Don’t know anything about undervolting… but will that be my only hope with my current config, or is it possible I could squeeze in as is? From earlier post, someone said that 280x should be about 280W each and then rest of the system maybe 80W. Based on those numbers, that would put me right at 1200. Please advise- thanks!
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I’ve got 3 rigs running 4 Sapphire 280x’s, they pull 1100 watts at the wall and a Seasonic 1250w PSU happily supplies each one. That’s undervolting to 1.075 each card…
Providing the weather stays cool, I have no issues. However during the hot days in the Aussie summer I was getting all sorts of issues, so I pushed the voltage up to 1.113 per card and I got rid of the errors.
I found that interesting, I needed to bump up the volts in the heat to get stability… Don’t understand it but it worked…
To answer your question, yes you’ll be fine with a 4th card with a bit of undervolting…
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Thanks, I appreciate the info ;D
