980Ti SLI owners - Call for power draw measurements

[norritt]

Hey everyone,

 

I'm thinking of upgrading my system with a 2nd GTX 980Ti. Problem is that my 600W PSU originally wasn't chosen to power a SLI system. Anyhow knowing that people usually tend to *way* overestimate the power usage of their systems I did some research. According to tomshardware a single 980 Ti, when stressed will use no more than 254 Watts. According to these numbers a system using my CPU (i7 3770k) will consume around 166 Watts under load. Adding up these numbers we'll get a:

 

Total power draw from the wall = 2*254Watt + 166Watt = 674 Watt

 

Since even decent PSUs are not 100% efficient but rather have an efficiency factor of somwhere between 87 - 90% the effective power usage will be between:

 

p_87 = 674 Watts * 0,87 = 586,38 Watts (@87% efficiency)

and

p_90 = 674 Watts * 0,9 = 606,6 Watts (@90% efficiency)

 

Which will be pretty much spot on what my PSU can deliver. Considering that the above wattages have been measured synthetically using stress tests like Furmark, and the gaming load on tomshardware has been measured with 233 Watts per card rather than 254, the extreme power draw of 586 to 606 Watts will not be reached reagularly/continuously.

 

Adding up these numbers out of two different sources to calculate wattages are just a pretty rough guesstimate. If anyone of you owns a 980 Ti SLI system and a power meter, I would be really interested in a measurement of the real peak power draw of your system running stress tests for CPU and GPU at the same time (i.e. Prime95 and Furmak).

[Nacho Marco Segui]

Which psu

[Darel321]

ehh.. no matter how good that psu is.. I doubt its gonna run 980ti sli... its gonna be rly close to its limit.. and its not a good idea to do that...

[BbsMentos]

I have a friend who has a RM850X and runs a 980t iSLI on It with no problems what so ever so 850W 80+Gold should be fine

[Morgan MLGman]

750W is recommended to SLI two 980Tis, though I think 650W would suffice tbh. Wouldn't recommend running it on a 600W PSU.

[norritt]

17 minutes ago, Nacho Marco Segui said:

Which psu

 

Here is the vendor page: http://cougargaming.com/products/power_supplies/cougar_gx_v3.html

Also there is a review on this PSU by JonnyGURU, if you're interested in more details (Unfortunately he only reviewed the 800W version): http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=305

 

I'll take a look if I find a review of the 600W Unit. Anandtech also reviewed Cougar but also only the bigger units (1050W).

[DXMember]

if you don't do crazy overclocks on both CPU and GPU, you'll be just fine with 600W

[norritt]

FYI: I just found this video on youtube measuring the power draw of a 980Ti SLI System running Crysis 3 on max settings. While in this scenario the power draw stays well below 600W (as expected), Crysis 3 will neither stress GPU nor CPU to 100%. So if anyone is able to deliver measurements of his 980TI SLI system under synthetic stress I'd be grateful for some numbers of what can happen in the worst case scenario.

[Rune]

Efficiency calculations would require more wattage, not less. A 750 watt PSU at 90% efficiency would deliver 674 watts.

[norritt]

1 minute ago, Rune said:

Efficiency calculations would require more wattage, not less. A 750 watt PSU at 90% efficiency would deliver 674 watts.

No, 600W is the amount of power the PSU is able to deliver to the system, this means after AC to DC conversion. So the amount of power drawn from the wall will always be higher than what is actually delivered to the system. Some shoddy vendors might label their PSUs according to how much power they will draw from the wall but no reputable PSU vendor will do so.

[iDeFecZx]

My friend runs a pair of 980Ti MSI Gaming cards off an RM650x with no issues

[Quaker]

24 minutes ago, Rune said:

Efficiency calculations would require more wattage, not less. A 750 watt PSU at 90% efficiency would deliver 674 watts.

You've got it backwards. A 90% efficient 750watt PSU would draw 830 watts from the wall to provide 750 watts output. Power supplies are rated for their output power, not their power draw.

[Kryptyx]

While it may work, I would recommend getting a little more head room. I have a Corsair AX860i with my 980TI sli setup.

[norritt]

2 minutes ago, Kryptyx said:

While it may work, I would recommend getting a little more head room. I have a Corsair AX860i with my 980TI sli setup.

Yes usually, I'd be on the same page here. The reason I'm considering upgrading to SLI is that due to the 1080 Release the price of the 980Tis dropped so you I could grab another card on the cheap. If I go and buy another PSU with lets say 850W for around 200 bucks, the "cheap upgrade" argument will be kind of invalid.

 

Also having done the reasearch I'm actually genuinly curious how much power a PSU really has to deliver to a 980Ti SLI system.

[App4that]

This is a good video for this topic, Kevin shows the power draw on the SLI configuration.

 

 

[Anarchyz11]

I run 980ti SLI on an HX850.  Could you run it on a 650W PSU?  Probably, if the power supply is decent quality.  Would I?  Never.  Not gonna cheap out on the component that can fry $1,000 of hardware in an instant.  Get a decent power supply and it'll last you multiple GPU lifespans.  

You can get a solid 750-850W PSU for $100-$130~, $200 seems a bit excessive if you're on a budget.

 

[Kryptyx]

34 minutes ago, norritt said:

Yes usually, I'd be on the same page here. The reason I'm considering upgrading to SLI is that due to the 1080 Release the price of the 980Tis dropped so you I could grab another card on the cheap. If I go and buy another PSU with lets say 850W for around 200 bucks, the "cheap upgrade" argument will be kind of invalid.

 

Also having done the reasearch I'm actually genuinly curious how much power a PSU really has to deliver to a 980Ti SLI system.

Okay, this makes more sense. I think you'll start stressing the PSU with that setup and you won't really have room for overclocking which is a loss in performance you should also factor in. I'm no PSU expert though, ask around on the PSU thread.

 

@Comic_Sans_MS

[norritt]

37 minutes ago, Anarchyz11 said:

I run 980ti SLI on an HX850.  Could you run it on a 650W PSU?  Probably, if the power supply is decent quality.  Would I?  Never.  Not gonna cheap out on the component that can fry $1,000 of hardware in an instant.  Get a decent power supply and it'll last you multiple GPU lifespans.  

You can get a solid 750-850W PSU for $100-$130~, $200 seems a bit excessive if you're on a budget.

 

Well it's not actually about cheaping out. The 980Ti SLI is nice to have but IMO not worth the additional PSU upgrade.  As you can see in the video I linked above the 980Ti SLI Setup running Crysis 3 on 90-95% load on both SLI GPUs only seems to require at most 511 Watts to be delivered by a PSU.

 

@App4that: Awesome, thanks for the link. Apparently "TechShowdown" has measured a maximum power draw from the wall of about 611 Watts. Assuming his PSU has an utopian efficiency of 95% this means the actual power draw of his system was ~575W under full stress. If we assume a more likely 90% efficiency it would even be only ~550W. If those numbers are correct one should not be able to overload a 600W PSU with a 980TI 2-way SLI (except maybe with crazy OC's or using Hexa-/Octacore CPUs).

 

[KWelz]

I can help here with some real world testing.  I have ben getting Sudden Shutdowns on my system with the cards overclocked so I put a Kill-o-watt on it to measure draw just a couple days ago.   

 

I am running a 5820K Oced at 1.275V and two EVGA 980Ti SC+ models.   

 

At full running Firestrike with the GPUs not OCed I was pushing 750Watts at times.   If I put any OC on them this would spike closer to 800 before the system would shut down.   My conclusion is that my AX860 is at best borderline for this type of configuration and it is time to upgrade to a 1000 Watt of some sort.  

[norritt]

@KWelz: Thank you for sharing your experience with the 980Ti's (I'm actually using the same model here). I find it very interesting that you ran into those problems, since your power usage seems to be *way* higher that what I've been able to dig up on the internet. Anyhow even if you are spiking up to 800W powerdraw from the wall, factoring in the rated 92% efficiency, your AX860 only had to deliver 736 Watts during those spikes.

 

So while your shutdowns definitly point to a problem, it is probably not because 860 Watts aren't sufficient though. Maybe Corsair's design actually can't deliver 800 Watts (but I doubt that TBH), or there is something wrong with your particular unit. I mean the 980Tis are rated at 250 Watts so with 1kW your pretty much already in the 3-way SLI region with 3*250W = 750W leaving you another 250W for the rest of the system plus optional overclocks.

 

If you still have warranty for the AX860 I'd try to RMA it first before shopping for a bigger PSU. Anyhow I'm very interested in hearing how your troubleshooting continues and what will have finally resolved your problem in the future.

 

Getting back to my case - Your numbers are actually the first ones I found discouraging the idea of powering 980TI SLI with a 600W PSU only. 736W is definitly *way* too much for my PSU.

[KWelz]

You are probably correct. A month or so ago I was actually having some issues where the Asus anti-surge protection on my motherboard was triggering. Corsair told me it was a false reading, but now I kind of wonder.   

 

Even with my CPU pulling around 130 W I should be OK you're right.

 

 I will probably go ahead and RMA it at this point. Truth be told I need another PSU anyway, so I'll get a better unit for my main rig. And then move this to my secondary computer that I am working on. 

[norritt]

1 hour ago, KWelz said:

Truth be told I need another PSU anyway, so I'll get a better unit for my main rig. And then move this to my secondary computer that I am working on. 

If you got your new PSU and got the time send me a notice how it performed and how much power it did draw compared to your AX860.

 

Have you already decided which PSU it is gonna be? One of my favourites in case I decide to upgrade to 980 Ti SLI and 600W are not enough would be the bequiet Dark Power Pro P11 (But I'd probably go with the 850W version not the 1kW version I linked, just because I really think 1kW is way overkill). Another candidate I like which is not that expensive is the Enermax Platimax.

[KWelz]

I am a big fan of EVGA power supplies, so I was probably going to go with a 1000W P2.

 They are hard to meet for the money. 

 

 I will probably pick it up this weekend, when I do I will update this thread with any information I get. 

[KWelz]

Just thought I would report back.   I ended up getting an AX860i model for a good price.   Tested power draw using Corsair link this time.   Max reporting in system with CPU and both GPUs overclocked was 730 Watts system usage with 806 being pulled from the wall.       

[norritt]

@KWelz: Awesome, thanks for the update =)