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Is 850 Watt enough for 2x R9 290x GPUs?

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davidst99

Senior member
Hi,

I have a SeaSonic 850W PSU. Is it enough to power an overclocked I7 4770K, 2x R9 290x GPUs (factory overclocked to 1040Mhz), 1 SSD and 2 HDDs? If not, how big of a PSU would I need? I searched Google and everyone has a different opinion about how big your PSU should be Thanks for any help.

David
 
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Yes if you don't OC the CPU and GPU's. You can probably OC to a to the MAX under Air but not under water. Say at 1.35 to 1.5v Volts CPU at 4.4Ghz's and the R290X's at 1130x 1500 but don't expect more with out things throttling over Hi-Temps and Protection Reboots.

If you OC with Water Cooling you need at least a 1000w PSU that is Running 1 or more Pumps and say 6 x's Noctuia 140 mm Fans. I run my i7 2700k at 4.8Ghz's and 2 x's 290X's XSPC's at 1180 x 1500Mhz's (F*^k Elpida) - 24/7 - Everything under 50C approaching maximum load - Idling at 34C for the CPU and 32C for the GPU's. I run an XFX BEFX 1050W Black Edition PSU KM3 Designed PSU with Water but my XFX 850W Black Edition (Same as your unit - Both KM3 Designed) would Crossfire 290X set nicely under Air (Rather Noisy - Less Voltage and Less Mhz's).

I can run a single OEM 290X at 1280 x 1500Mhz (Elpida) with no throttling under water. X-Fire is another matter where you have to config each GPU separately to achieve a common zone at say a +0.142mV Offset - MAN it's FAST on a QNIX 2510 Evo II Dvi-D at 120 Hz's.

Yes your PSU will do AIR but if you want to go under water and run Cooler, Quieter with more Voltage and MHz's you need more Watts considering a KM3 850W PSU will reset at 955 Watts.
 
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Z15CAM,

Thanks for the reply and information. I don't plan on overclocking my GPU more then the factory overclock speed. I overclocked my I7 4770K to 4.2 Ghz at 1.175V. I don't have the expertise to install water cooling.

David
 
Go ahead, under AIR, but you will become board with your 850W KM3 throttling 290X's in X-Fire Under AIR when you know you can handle a lot more voltage with X-Fire 290X's and keep your system cool and quiet without throttling Under Water.
 
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are you buying this PSU, or do you already own it? and if you are buying it, which one are you buying?

besides the fact that "850w psu" means nothing (there are PUS which are sold as 850 but are barely 600w), getting a good one can be a major improvement over an average one. we can also help you get a good deal.

or you can ready jonnyguru.com <- try it!

edit: i must have dreamed it but i thought OP didnt write the brand.
 
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Ran the numbers for my OC 2500k, same drive configuration, 2x R9 290 on a Corsair CM750 but it would be probably 100w short of running in the sweet spot. You don't want to run most power supplies at exactly 100% because it starts to drop off in efficiency and get much hotter. But with a 850w from Seasonic and the 4770k I think you'll be fine. Just don't get too crazy with overvolting the 290s. You should be able to overclock as much as you can get on the 290s at stock volts.
 
So the consensus is that you will be fine with a KM3 850W PSU under Air if you don't over volt or OC much but it will be Noisy and probably throttle but you require at least 1000 Watt's if you Over-Volt and OC Hawaii Under water in Cross-Fire to be quiet and the GPU's don't throttle.
 
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I ran 2 r9 290's on a corsair 850w gold with an 8 core AMD and it did well even overclocked. However I always felt I was on borrowed time and wasn't comfortable until I bought a 1200. High power requirement pc's are a waste though imo. You should be able to build a beast under 750w, and this will be even more true with maxwell and broadwell.
 
Hi,

850w for 290x CF and overclocked i7 is cutting it real close.
I suggest a 1000w PSU, maybe CM V1000 * a seasonic OEM PSU.
You will have tons of headroom and its running at about 60% load all the time ...

cheers
 
Hey.
Not to highjack the thread, but have a similar question.
Running 4770k (not OC'd yet, will be soon), 2x 290X TRI-X OC cards that I will OC soon (though probably won't overvolt). Maximus VII Hero, SSD, couple of HDDs case fans and currently the NH-D14 (will be replaced probably with the NZXT X61 soonish). Powered by SeaSonic Platinum 860W PSU (about half way through the page). Will it cut it?
And I don't see the need to be running at 60% of the PSU as it's less efficient and unnecessary. I think I should be around 750-800W (by my calculations, reviews and an online PSU calc) which is ~90%.
Thanks for your advice (@OP - hope it's OK)
 
Yeah, thats fine UP. But running your PSU at 90 percent will wear it out fast enough to where I would highly reccomend getting a new PSU after 3 to 4 years.
 
Hmm. I'll check, maybe I'll sell it and get a new one.
How are TT Toughpower XT PSUs? Not a huge TT fan, but that is supposed to be their top of the line PSU series. I have an option of getting a TT Toughpower 1275. Wondering if it's worth the money or I should stick to SS or maybe go Corsair...
 
Jonnyguru said its fine: www.jonnyguru.com/modules.php?name=NDReviews&op=Story5&reid=298

But it doesn't win any awards, unlike the Seasonic Platinum 860/1000 which are both highly reccomended by Anandtech and win a Reccomended award from Jonnyguru. The eVGA Supernova 1000 G2 also wins a reccomended award.

OP and UP, 1000 watts is plenty. 300W x2 for the 290Xs, 100W (more or less) for a OCed 4770K, and maybe 60W to 100W for the rest of the system.

Like I said, your current PSU will work fine, but running it under such a a high load will wear it out much more quickly then a 1000W.
 
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PCunicorn said:
Jonnyguru said its fine: www.jonnyguru.com/modules.php?name=NDReviews&op=Story5&reid=298

But it doesn't win any awards, unlike the Seasonic Platinum 860/1000 which are both highly reccomended by Anandtech and win a Reccomended award from Jonnyguru. The eVGA Supernova 1000 G2 also wins a reccomended award.

OP and UP, 1000 watts is plenty. 300W x2 for the 290Xs, 100W (more or less) for a OCed 4770K, and maybe 60W to 100W for the rest of the system.

Like I said, your current PSU will work fine, but running it under such a a high load will wear it out much more quickly then a 1000W.
Click to expand...

Thanks! That's about what I calculated.
I'll try and see if the hard lockup I experienced was drivers (14.6) or maybe one of the cards.
I can buy the TT for about $150, which is what I (hope) I can get for mine. I do like SS though...
 
290x x2 factory oc + 4770k oc

as long as the psu is a reputable brand that is honestly rated for continuous power. seasonic is indeed.
850watt you got is enough.


tweaktown - 290x cf stock + 3930k oc - full system on 3dmark11 drawing 750w from the wall (675w from ax1200 gold psu 90%)
hardocp - 290x cf stock + 3770k oc - full system on gaming load drawing 733w from the wall (660w from erm1350 gold psu 90%)
hardocp - 290x cf oc volt + 3770k oc - full system on gaming load drawing 833 from the wall (750w from erm1350 gold psu 90%)


.
 
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it should be enough, though perhaps with very heavy overclocks on everything plus a well optimized application, you could actually reach 850 watts.
 
@UP - you have your idea of "efficiency" wrong.

PSUs will run most efficiently around 50~70% of their rated wattage, depending on the quality of the PSU. Getting closer to the maximum rated wattage will generally result in a much lower efficiency.

Two things you have to see here. The first is that PSUs have a maximum rating.
A 1000W PSU doesnt use 1000W, it uses whatever wattage you draw from it. 1k is just the maximum it can handle.

Second is efficiency. If a PSU was 100% efficient, when you draw 500W from the PSU, the PSU draws 500W from the wall.

This doesn't happen; Generally most modern, high end PSU will "burn" around 10% of the energy they take from the wall in the form of heat, thus they are rated "90% efficient".

example;

a 90% efficiency PSU attached to a PC, the pc draws 500W from the PSU, the PSU draws 550W from the wall.
Your PC gets 500W, the extra 50W go in the air as heat.

Now, the efficiency rating of a PSU depends on the load you put on it.
A normal 700W PSU might have for example, 90% efficiency at 500W, but only 80% at 650W.
This means that when you push a PSU near the rated maximum, you will spend more on electricity as it needs to draw more from the wall to get to the wattage your PC is asking.
Also, more heat -> less life from the components.

One final note, PSUs do have a minimal wattage too - if you try to use a 1000W PSU with a 100w PC, you will spend more. Typical PSUs perform their best around 50~70% of their rated W, with both much less and much more being less efficient.
 
Yea, if not OC'ing the GPU's that PSU is not going to be a likely culprit for any lockups. Having $20-30 power meter like a Kill a Watt meter or the one from Belkin, really helps for this kind of thing. I'd guess you are using 650-700 watts peak of your PSU, drawing no more than ~770w peak from wall.

I ran 290 (non x) crossfire at 1040/1350 with +50mv overvolt with a 4690k 4.4 1.26v and peaked at wall at 689w, I have a platinum PSU that was 90% efficient so I was using around 620w from the PSU. Plenty of headroom for quality 850w unit.

My psu is a corsair ax860, a seasonic unit. It idles at 60w from the wall, so I can't be sure, but I think it remains pretty efficient throughout it's delivery. Johhnyguru does a good job testing PSU's at various loads, which can give you better idea of certain PSU's capabilities.
 
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PSU 850 Watt is enough for 2x R9 290x.

You can OC 4770K.

Anandtech review 2x R9 290x with system Intel Core i7-4960X @ 4.2GHz

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Remember TDP 4960X is 130W but TDP 4770K is 84W.
 
My advice is give yourself more headroom. You just don't know the strain on all your components you may be causing over time, even though on paper is should be OK. Overclocked CPU and 2 overclocked cards that are going to have fans running at full speed, plus who knows what else can be going on in your system. If you have 2 GPU cards that each require 2 8-pin power cables, you are not in Kansas any more...Get a top rated 1000W PS since you want to do this the right way. It is worth the peace of mind.
 
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