Total max system W=1120. 1400W PSU enough?

[Ghiddy]

It's this high mainly because I'm running 3 Radeon cards in it.

I added up the power draw for CPU, ram, SSD, DVD, etc, and that equals 1120. I'm aiming for an 80 Plus certified unit.

I added 8% to that figure just to give some padding, and then divided by .87 (to account for the PSU's efficiency, but not sure if this step was needed). So:

(1,120*1.1)/.87 = 1390.3W

So would I be safe with a 1400W PSU, assuming the 12V's had enough to power the cards? I'm not sure a 1400 will be enough though because when PSU's have multiple rails don't you get some unused leftover on each rail? For example if you plug in 1 vid card into a 40A 12V rail, and the card uses 29A, you have 11A leftover on that rail. 11A is not enough to put another card on the same rail. How do you solve this? Do you normally have to get a much bigger PSU than necessary so that the card power use fits onto the 12V's?

 

[BoomerD]

Are you sure you're not adding the total system requirements for each Radeon card? Most of the time, when a site lists power requirements, they're giving the total wattage for the system, not just the video card.
If you look at this graph:

You'll see what I mean...those numbers are for the total system...not just the individual video card.

You can try this PSU calculator:
http://extreme.outervision.com/psucalculatorlite.jsp

It's fairly accurate as long as the user is realistic with his hardware...it won't calculate 3 video cards, but with a bit of math...you can do the calcs for a single card, then for Crossfire ...and calculate the difference...and add it to the numbers for the Crossfire config.

 

[Ghiddy]

First, thanks for your response. I am pretty sure my addition is correct for the cards, and I wasn't using stats for the whole system. See here for power consumption for a full system with a single 6990 is 550W. http://www.anandtech.com/show/4209/amds-radeon-hd-6990-the-new-single-card-king/18

My CPU and ram are minimal since I'm mostly using this for folding and to try to mess around with OpenCL development.

And I did see that power calculator page before my OP, but I am suspicious of it because it reports that I need a pretty low PSU. Even when I put in that it will be at 100% load. And I did do the thing where I do the difference between a single card and crossfire to try to extrapolate the power for 3 cards. It seemed off, which is why I ended up posting here.

 

[BoomerD]

If those numbers in the link are accurate, you don't need a power supply, you need a nuclear plant...I'm not sure even a 1500 watt PSU will have enough wattage on the individual rails for those...

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=175

Also, Enermax is supposed to have a 1500 watt version of their MaxRevo that's pretty decent.

 

[theAnimal]

It's this high mainly because I'm running 3 Radeon cards in it.

I added up the power draw for CPU, ram, SSD, DVD, etc, and that equals 1120. I'm aiming for an 80 Plus certified unit.

I added 8% to that figure just to give some padding, and then divided by .87 (to account for the PSU's efficiency, but not sure if this step was needed). So:

(1,120*1.1)/.87 = 1390.3W

So would I be safe with a 1400W PSU, assuming the 12V's had enough to power the cards? I'm not sure a 1400 will be enough though because when PSU's have multiple rails don't you get some unused leftover on each rail? For example if you plug in 1 vid card into a 40A 12V rail, and the card uses 29A, you have 11A leftover on that rail. 11A is not enough to put another card on the same rail. How do you solve this? Do you normally have to get a much bigger PSU than necessary so that the card power use fits onto the 12V's?

If you're going to be drawing 1120W, I'd recommend a 1500W PSU. As for the rails, read the sticky. If a PSU has separate rails, then there will only be 2 PCIe connectors per rail.

since I'm mostly using this for folding and to try to mess around with OpenCL development.

I don't know much about OpenCL, but for folding Nvidia has a big advantage over ATI. Also hope you would consider joining TeAm Anandtech Folding@Home.

 

[hardboy]

For 6990 trifire get at least 1500 to 1600 or more
Also I dont think ati drivers allow quadfire leave alone hexafire. Get 6990 plus 6970 max.and that too wont have good support. Best to get two 6970 oc

 

[bobwagner]

I seriously doubt that you need that much wattage. Here's why: I just bought a kill-a-watt to see what my system draws. With Prime95 AND Furmark both running at full blast, I saw a peak of only 550w. My relevant specs:

2600k @ 1.2v
4x4GB RAM
120GB SSD
500GB HDD
2x 6970 CF
HX850 PSU

So with all CPU cores at 100% and all GPU cores at 100%, I still only drew 550w AT THE OUTLET. My PSU runs at 90%+ efficiency in that range so my system was only drawing around 500w. To extrapolate, you can run TWO of my systems on a 1000w PSU...and two of my system is several hundred watts greater than your planned setup.

I think there's a tendency nowadays to go overkill on the PSU. Had I known what I know now, I would've gotten a 750w PSU. You'll be just fine with a high quality 1000w PSU.

 

[Ghiddy]

I seriously doubt that you need that much wattage. Here's why: I just bought a kill-a-watt to see what my system draws. With Prime95 AND Furmark both running at full blast, I saw a peak of only 550w. My relevant specs:

2600k @ 1.2v
4x4GB RAM
120GB SSD
500GB HDD
2x 6970 CF
HX850 PSU

So with all CPU cores at 100% and all GPU cores at 100%, I still only drew 550w AT THE OUTLET. My PSU runs at 90%+ efficiency in that range so my system was only drawing around 500w. To extrapolate, you can run TWO of my systems on a 1000w PSU...and two of my system is several hundred watts greater than your planned setup.

I think there's a tendency nowadays to go overkill on the PSU. Had I known what I know now, I would've gotten a 750w PSU. You'll be just fine with a high quality 1000w PSU.

What you say makes sense. But I am puzzled because I went by the max TDP ratings of the components I got. The video cards themselves are over 90% of the total rating, and doing folding on them should take them to the max power usage they are capable of no? I also got an 80 plus gold PSU. I have a feeling I over did it with the PSU (ended up getting a 1200W). I'd rather be safe with this anyways. The PSU is one part I won't cheap out on.

 

[CLite]

I think there's a tendency nowadays to go overkill on the PSU. Had I known what I know now, I would've gotten a 750w PSU. You'll be just fine with a high quality 1000w PSU.

Your build has 2 GPUs, his has 6......

He probably needs more than a 1000w PSU.

 

[dualsmp]

Two 6990's use 886w from the wall over at HardOCP. I suppose a third one will be close to 1261w from the wall if you add another 375w. Might be around ~1100w (DC) is my guess so a 1200w PSU should be enough.

http://hardocp.com/article/2011/05/19/quadgpu_performance_review_nvidia_vs_amd/8

 

[bobwagner]

Your build has 2 GPUs, his has 6......

He probably needs more than a 1000w PSU.

Oh sweet baby jesus. I thought by "3 card," he meant the 6990 + 6970 trifire setup (3 gpus).

Ok, if you're gonna rock 3x 6990 then yea, you'll hit 1000w.

 

[killster1]

You know u can always run two psu's..

 

[pcunite]

So would I be safe with a 1400W PSU, assuming the 12V's had enough to power the cards?

Please buy a P3 Kill-A-Watt meter and tell us how much your system is really drawing from the outlet. I would love to know.

 

[TemjinGold]

If you just wanna fold, have you considered just building 2-3 computers instead? Would likely be cheaper and less power hungry to achieve the same...

 

[theAnimal]

If you just wanna fold, have you considered just building 2-3 computers instead? Would likely be cheaper and less power hungry to achieve the same...

If it's strictly for folding, then build a quad CPU AMD system.

 

[LiuKangBakinPie]

It's this high mainly because I'm running 3 Radeon cards in it.

I added up the power draw for CPU, ram, SSD, DVD, etc, and that equals 1120. I'm aiming for an 80 Plus certified unit.

I added 8% to that figure just to give some padding, and then divided by .87 (to account for the PSU's efficiency, but not sure if this step was needed). So:

(1,120*1.1)/.87 = 1390.3W

So would I be safe with a 1400W PSU, assuming the 12V's had enough to power the cards? I'm not sure a 1400 will be enough though because when PSU's have multiple rails don't you get some unused leftover on each rail? For example if you plug in 1 vid card into a 40A 12V rail, and the card uses 29A, you have 11A leftover on that rail. 11A is not enough to put another card on the same rail. How do you solve this? Do you normally have to get a much bigger PSU than necessary so that the card power use fits onto the 12V's?

lol post your specs your going the wrong way