Confused with size of PSU for GTX 680 SLI

Vipermk2 · Feb 23, 2013

I've just got a Asus GTX 680 and while I have some money thought I'd get another one just to prepare me for future games with even higher quality graphics.

The problem I'm having is to whether my existing Corsair AX 850 is enough. There seems to be conflicting information on 3 PSU calculators.

The first one I used was on the ASUS Website. Then went to the Extreme and Thermaltake power calculators.

All 3 give different power ratings, any ideas on this one, is there something about the ASUS card that the other 2 don't take into account.

Extreme

Thermaltake

TwoCables · Feb 23, 2013

For some reason, the Thermaltake calculator is the most accurate one here yet it's still overkill. Change "System Load" to 75% because this is a much more realistic figure for gaming unless you are Folding or BOINC'ing 24/7. Also, capacitor aging is really not an issue with the AX850, so undo that option (it's really only an issue with lower quality PSUs due to using lower quality caps). After these 2 changes, it should come out to be roughly 675W, give or take about 10W which is about where it should be.

Vipermk2 · Feb 23, 2013

Thank you for your speedy reply and I much appreciate your opinion, I'm trying to get a grip with this because the ASUS specs for the card says,

'Power Consumption up to 300W additional 6+8 pin PCIe power required'

If I have 2 running wouldn't that mean it would require min of 600w or is it somehow less than x 2 because of the SLI.

TwoCables · Feb 23, 2013

Vipermk2 said:
Thank you for your speedy reply and I much appreciate your opinion, I'm trying to get a grip with this because the ASUS specs for the card says,

'Power Consumption up to 300W additional 6+8 pin PCIe power required'

If I have 2 running wouldn't that mean it would require min of 600w or is it somehow less than x 2 because of the SLI.

You're welcome!

I don't see how they figure it could pull up to 300W unless they're talking about the entire system's power draw at the wall outlet:

GeForce GTX 680 SLI review - Power Consumption

One GTX 680 under full load in their system caused their PSU to pull 307W from the wall outlet.

Now, with two GTX 680s under full load in their system, their PSU pulled 473W from the wall outlet. Their CPU was idling, so I have to add up to 130W for the i7-965 under full load which would then make the PSU pulling 603W from the wall outlet. So if the PSU is pulling 603W from the wall outlet under full load, then the system is only pulling 512W from the PSU.

So figuring in everything else, and I would say it should add maybe 100-150W at the most.

Vipermk2 · Feb 23, 2013

Thanks again for the information, reading further into that article it may indicate that I will be borderline with the power as they do say,
'GeForce GTX 680 SLI - On your average system the cards require you to have a 750 Watt power supply unit as minimum.'

I would say my system is slightly above average and I do have my i7 3.2 O/C @ 4.2 which you cant see in the images in the first post.

TwoCables · Feb 23, 2013

Vipermk2 said:
Thanks again for the information, reading further into that article it may indicate that I will be borderline with the power as they do say,
'GeForce GTX 680 SLI - On your average system the cards require you to have a 750 Watt power supply unit as minimum.'

I would say my system is slightly above average and I do have my i7 3.2 O/C @ 4.2 which you cant see in the images in the first post.

I know, but the kind of 750W power supply they're talking about is a peak-rated unit. Most peak-rated 750W power supplies have a continuous capacity that's closer to about 525-550W.

A quality-made 550W has a continuous capacity of 550W.

Vipermk2 · Feb 23, 2013

Thank you very much for sharing your knowledge it will definitely help me choose whether to get another 680

TwoCables · Feb 23, 2013

You're welcome, Vipermk2!

bobkn · Feb 23, 2013

nVidia has a list of SLI certified PSUs:

http://www.geforce.com/Active/en_US/en_US/pdf/PSU.pdf

No 680 SLI, even though they list the 690.

The Asus GTX680 that you list may draw more power than the reference 680. I have one of those, with two 6 pin PCI-E power connectors. (The PCI-E slot is rated up to 75W. A 6 pin connector is rated at 75W. 8 pin 150W.) The Asus unit has a 6 pin and an 8 pin. Either the Asus needs more than 225W peak (up to 300W), or they're messing with our heads.

My guess is that the AX850 (70A at +12V) ought to be OK, although it may not have the margin that some of the fanatics here would want, if you're overclocking a 125W (stock) CPU to the ragged edge.

kbrady1979 · Feb 23, 2013

Trust TwoCables on this issue. Your AX850 will run an OC'd CPU, dual 680's and all of your other components just fine. These new components are much more powerful than older components, but require quite a bit less power to run. If you want another 680, you might be in luck.......I have a feeling they will be dropping in price soon.

bobkn · Feb 24, 2013

kbrady1979 said:
Trust TwoCables on this issue. Your AX850 will run an OC'd CPU, dual 680's and all of your other components just fine. These new components are much more powerful than older components, but require quite a bit less power to run. If you want another 680, you might be in luck.......I have a feeling they will be dropping in price soon.

Just for fun, I looked up a review of the Asus card:

ASUS GeForce GTX 680 DirectCU II OC | silentpcreview.com

Looks like it doesn't use much more power than a reference GTX680 at maximum load. The 300W capacity of its PCI-E power connectors isn't needed. The two cards together would only use roughly half the capacity of your AX850.

Go for it.

Vipermk2 · Feb 24, 2013

Thank you all for adding your opinions and advice, looks like I'll be going for another card soon.

TwoCables · Feb 24, 2013

Sweet! More GPU power!

Wishmaster · Feb 24, 2013

The Ax series are basically a Seasonic X series PSU.
These are very good Power Supplies (Gold rated) and the advertised wattage on these units are typically its continuous output.

While not all PSUs may be able too, a AX750 or X750 should be able to run SLI 680s without much issue, although it may get tight if Overclocking them.
And have no issues with SLi 570/670s.
The 750 variant can peak around 1K output for a short time.

An AX850 will have additional Headroom and should run SLI 680s without any worries.

You'd be OK even at 750 if not OCing.
With a AX850, I wouldnt think twice about it. It'll be fine.

Confused with size of PSU for GTX 680 SLI

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