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850 W PSU good enough for two GTX770s?

post #1 of 14
Thread Starter 
Hello,
I found all kinds of contradictory information on this, so I thought I would ask because I have an unusual configuration that is not for games, in fact I don't have any games in my computer.

Right now I have a CORSAIR Enthusiast Series CMPSU-850TX 850W with a GIGABYTE GV-N770OC-4GD GeForce GTX 770 4GB and a GTX570 1.2 GB. The idea is to pull out the GTX570 and add another GTX770, the same exact model. These will not be in SLI because I need them to render 3D with a software called Octane, which uses both cards but can't work in SLI.

The way this program works, the CPU is barely used at all (8% at the most), while the GPUs are used at the maximum. In the case of this GTX770, the description says it's a 450W card, but I don't know if that really is a real number or some nominal figure just to impress people. Obviously if it's a real number my PSU it won't work with two, but I wanted to see what the experts here think.

In case I need to buy another PSU, is 1000W good enough or should I go higher? And, since good ones at this wattage are very expensive, is Rosewill a decent one? I know they make cheap products, some of which are well rated and others poorly rated, but you know how those things are, I found great products by cheap brands and viceversa. For example this one:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817182188

Would it be good enough? My system specs are:

CPU: i7 3930k
RAM: Corsair Dominator 32 GB
Motherboard: Asus P9X79 Pro
SSD Samsung EVO 840 500 GB
HDs: 2 Seagate Barracuda 3 TB, 1 WD 1 TB
2 Blu-ray drives, LG and Pioneer
Graphics cards: 2x GIGABYTE GV-N770OC-4GD
1 small Matrox card that has a port to connect to a A/V breakout box, sandwiched between the two graphics cards.

Thanks for any advice. I hope you don't mind if I post this on a few other forums, I just need an answer as soon as possible.
post #2 of 14
The GTX770 is actually a 230W part.

Source:

http://www.geforce.co.uk/hardware/desktop-gpus/geforce-gtx-770/specifications

Sure if you overclock & overvolt it may go higher, but the '450W' you;re seeing is the cooling capacity of Gigabyte's Windforce 3X cooler.


850W is plenty for GTX770 SLI (or in your case, non-SLI wink.gif ), even when at load.
post #3 of 14
Thread Starter 
Thanks very much for your reply. So if the card itself is 230W, but the Gigabyte model says 450W, is the extra consumption because of those three fans? In that case, wouldn't it still be above what my 850W PSU can handle?
post #4 of 14
Most definitely. 850w is plenty.
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post #5 of 14
Quote:
Originally Posted by sebaz View Post

Thanks very much for your reply. So if the card itself is 230W, but the Gigabyte model says 450W, is the extra consumption because of those three fans? In that case, wouldn't it still be above what my 850W PSU can handle?

The 450W you're reading is specifically talking about the cooling capacity for the Gigabyte's custom cooler.
It doesn't use 450W, but the cooler is able to dissipate 450W worth of heat.

So essentially the cooler could almost cool TWO GTX770's on it's own.


The Gigabyte card is still a 230W part smile.gif
+
post #6 of 14
Im running 2 windforce 7950s on a quality 750W PSU with no issues at all.
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post #7 of 14
It's not a "230w" part strictly, it has a 230w "TDP". TDP is not equal to power consumption - in this case, it's basically just stating the default power limit - the card will throttle away from boost clocks, and eventually below base clocks if it hits those numbers.

230w is extremely conservative though for this silicon*, and since you can't really overclock these things (they come at stock 1.2v and it's very difficult to get them over 1.212, which is functionally almost identical) then you're fine with about 200 watts each at max OC (which is about 1300mhz@1.212v, 7600 on the memory error-free)

*gtx770 has 8 smx, 750ti has 15smx! It doesn't consume 450w at 1.212v, not even remotely close (default power limit is ~270w)

If you take 2x 200, assume 200w for the CPU (dunno how you're pushing your cpu) then that'd be about 80% utilization of a 750w psu at peak, which is where you should aim for. 850 is safe, though. I'm not really sure how much power you can realistically draw with a 3930k, but it sounds like you'd run fine on a 750w
Edited by Cyro999 - 4/20/14 at 12:39pm
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post #8 of 14
Thread Starter 
Excellent, thank you all for your replies, I'm so glad I don't have to order and install another PSU, I was not looking forward to that!
post #9 of 14
Yup 850w is enough. I had a 750w PSU and two MSI gaming 770's at 1.340mv, plus a 3770k at 4.9Ghz 1.420v
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post #10 of 14
Thread Starter 
BTW, the PSU only has two of those connectors that go in the back with the 4 and 6 pins, so using the molex adapters that are bundled with the card shouldn't bring any problems, right? Those old molex connectors seem so fragile, I always try to use them as less as possible.
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