Will my power-supply handle two GTX 780 Ti's?

[Kuroneko]

Hello my friends!

Right now, I'm getting an offer within about two months to get a second GTX 780 Ti for 1/3rd the price. However, I do not wish to upgrade my powersupply.

Build:
Intel i7-4790k @ 4.00 Ghz (No Overclock, just turbo)
ASRock Z97 Extreme4
8GB HyperX Fury 1866Mhz Memory
1TB HDD
128GB Crucial SSD
Corsair HX850w PSU.

Now, I have used a few PSU calculators that point towards me having a lot of headroom (still) with two GPUs, but I've read in a few places that this actually isn't enough to power the system.

I would like a few extra opinions before I decide on purchasing another 780 Ti.

~Kuroneko

 

[T-Bob]

Theoretically YES, as long as you don't overclock anything. With that being said I personally would not do it because you will be putting a major stress on your psu. I would recommend getting a 1000w psu.
Also you can always sell your current psu and purchase a higher wattage unit. If you watch for deals you can find good 1000w units in $100 range.

 

[OneMoar]

more then enough
you don't need a 1000W psu even if you where to overclock the cpu

 

[newtekie1]

The HX850 will easily handle your rig, with overclocking.

However, when you add the second card, make sure you plug in the molex power connector above the first PCI-E port.

 

[64K]

Your PSU can handle it but why? You're already rocking along with a GTX 780Ti Classified at 1080p. Unless your monitor is 120/144 Hz then you won't gain much. If you do buy the second 780Ti then let those beasts go to work on a 1440p monitor.

 

[OneMoar]

Your PSU can handle it but why? You're already rocking along with a GTX 780Ti Classified at 1080p. Unless your monitor is 120/144 Hz then you won't gain much. If you do buy the second 780Ti then let those beasts go to work on a 1440p monitor.

if hes gonna use DSR then the extra grunt might come in handy else i agree

 

[Jetster]

Yes with ease

 

[the54thvoid]

Yes. And no.
If you over clock them by much they'll require more power. I have two classifieds under water and heavily over clocked they shut down my 1000w seasonic.
Guys giving advice ought to checkup the Kepler power draw when passing certain voltages.
A 780ti over clocked on volts can easily pass 300 watts. Times two, add a CPU and you're hitting the limit fast.

 

[Frick]

Guys giving advice ought to checkup the Kepler power draw when passing certain voltages.

Point us to it. Besides, you're under water and you have the kind of cards that are sort of meant to do that sort of thing, OP might not.

EDIT: Was it Furmark btw?

 

[the54thvoid]

I'm on mobile so can't see OP's system spec but I thought I saw a ref to Classys.
Running Heaven Bench at 1.35v on sli with a 3930k at 4.4 GHz (1.4v) shut my system down. I'm not a noob and have pushed my cards hard for benching (at a very modest hobby level).
I learned my flashing and voltage info from the initial Titan volt modding forum on OCN.
Fact is, GK110 drinks power when you start upping volts. Kind of why Nvidia lock the voltage.
So, my answer stands. 850watts is enough based on low over clock and his current CPU. But if he ever wants to play with voltages and try water cooling then not enough power.
I'm limited by a very high quality 1000w PSU. I pushed 1.4v on my first Classy but with two in system, PSU can't cope at 1.35v.
I never use Furmark.

 

[Frick]

I'm not a noob

I know.

 

[the54thvoid]

I know.

Hugs all round.

 

[metalslaw]

It should be fine. Here are the two variants of the hx850(same name, old/newer model), and both can take over 300w on both rails without a problem.

http://www.hardwaresecrets.com/article/Corsair-HX850W-Power-Supply-Review/741/7

http://www.hardwaresecrets.com/article/Corsair-HX850-Gold-Power-Supply-Review/1602

EDIT : Rails are virtual, so only one 12v rail effectively, which doesn't make any real difference to the testing. The power supply can still take way over it's rating.

 

[newtekie1]

Yes. And no.
If you over clock them by much they'll require more power. I have two classifieds under water and heavily over clocked they shut down my 1000w seasonic.
Guys giving advice ought to checkup the Kepler power draw when passing certain voltages.
A 780ti over clocked on volts can easily pass 300 watts. Times two, add a CPU and you're hitting the limit fast.

Yes, they can peak right around 300w when overclocked on air, the 4970k might hit 175w when overclocked(but that is an over estimate really). That is still only 775w and I know from experience the HX850 can output that easily. He'll be on the edge of what the HX850 can do, but I don't think he'll have problems. Like you said, he probably will run into issues if he ever goes water and really starts pushing things though. But on air, I think he'll be fine.

I think part of your problem is your CPU as well. It can easily consume triple the power or more compared to the 4790k. And I've seen load power consumption with a 3930K go up 250w when pushing it. The 4790K is never going to do that.

 

[Kuroneko]

I think I may have forgot to mention this, but I will not be overclocking. I find the stock-speeds for my CPU and GPU just fine for what I need. If I ever decide to overclock, it'll be when I can get a new PSU.

So, with that in-mind, will I be fine?

 

[Frenzic]

You should be fine mate

 

[Kuroneko]

Thanks everyone for replying! I honestly want the two GPUs to somewhat future-proof my build. I'm currently in college and I'll doubt I'll be able to purchase any more parts in the next three years. And! If I decide to get with a larger monitor in the future, this'll help a bit in keeping the framerates up!

~Kuroneko

 

[Frenzic]

The only thing you should maybe consider as I was in the same boat as you, is the 3GB VRam for high resolutions, aa etc. All I'm going to do is go 120\140Hz with mine so they will be great for that and 1440p but yer, bare the VRam in mind if going to silly resolutions

Edit: DX12 might help with that, combining GPU VRam into a single pool.

 

[Kuroneko]

The only thing you should maybe consider as I was in the same boat as you, is the 3GB VRam for high resolutions, aa etc. All I'm going to do is go 120\140Hz with mine so they will be great for that and 1440p but yer, bare the VRam in mind if going to silly resolutions

Yep. I'm not planning on anything more than 1440p, cause 4k is a bit too expensive at the moment, and 1080p/1440p is just fine for me as long as I can max out the games .

 

[Frenzic]

Yep. I'm not planning on anything more than 1440p, cause 4k is a bit too expensive at the moment, and 1080p/1440p is just fine for me as long as I can max out the games .

Awesome mate

 

[the54thvoid]

Yep. I'm not planning on anything more than 1440p, cause 4k is a bit too expensive at the moment, and 1080p/1440p is just fine for me as long as I can max out the games .

Dual 780ti's wont show you much of a problem at 1440p in terms of Vram. I've only noticed problems using the 6GB texture res of Shadow of Mordor. If I use the ultra settings with textures on high (3GB+ memory requirement) my sli set up delivers awesome fps with almost no hitching at all.

Without overclocking and your cpu (as newtekie 1 rightly says) you'll be fine with 850w.

PS - you'll never future proof your PC. It's always a downward degradation.