SLI Power supply requirements

Well, this is the deal that has happened to me now. I have the EVGA 780i motherboard, 4G OCZ SLI memory, EVGA 8800 GTX ANS3 video card, 2 hard drives, 1 cd drive, 9 fans installed.

Everything works perfect with my Ultra 700 Pro power supply until I tried to go SLI today. I was a little worried that my power supply wouldnt be enough for this setup and went shopping for a good power supply that supports tri-SLI and was disappointed that my local computer stores didnt have a high end power supply with the specs I desired. I wanted a power supply that actually comes with 6 - 6 pin connectors for video power. There were none that I could find that were also modular. It makes no sense to me to pay 300.00+ for a power supply and have a rats nest to deal with.

I found the device some of you may be familiar with. The "juice box". It was the 450 watt version and mounts in a 5 1/4 bay and you plug one molex plug into it to power it on and the primary power cable for it goes out the back of the case thru a pci cover with a slot for the cable to fit thru and plugs into your surge protector. After installing this and checking all of my wires and making sure everything is good I decided it was time to power it on. Everything seemed to work fine, I was prompted to select SLI mode and then I ran a futuremark 06 benchmark and scored the same as if I was running a single card. That was late last night so this morning I was working more on the wiring and turned the system back on and it prompted me to set up sli again. I did and I decided to run futuremark06 again and scored under 7000 with very crappy frame rates. Later I got an error message that said it was detected that one of my video cards were not getting enough power and its performance would be reduced to compansate. I shut down the system and checked the wiring. I decided to call EVGA and the guy I spoke with recommended that I have at least a 750-800 watt for dual cards and 1000 watts or greater with 3 cards. Needless to say I took out the juice box and will be returning it tomorrow. You would think a dedicated 450 watt psu for a video card would be enough but this thing obviously doesnt work very well. EVGA said they sucked too so that confirmed my thoughts.

This makes me leary of trying to pigtail my connectors thru molex plugs to 6 pin connectors using just my 700 watt power supply. For one, its ugly as crap and the other I dont know if it will be good enough. From what EVGA support says its not, or may not be.

For now my extra card is sitting on the shelf anticipating my next move.

This is the power supply I have now:

The power supply I have my eyes on is this one (if I can find someone with it in stock):

I will only be running two of these cards until I can find a deal on a 3rd so this is practically a preplanning need.

My real purpose of this posting was to ask if anyone has a setup like mine with a similar power supply and have you had any issues with it?
7 answers Last reply
More about power supply requirements
  1. Absolute best power supply on the market, get it and be happy.
  2. You have a very good system which you are trying to run with a bargain basement PSU. Far too many people spend a lot of money on their systems and try to save money by skimping on the one component which every other component depends upon, solid, stable, adequate power.

    I doubt many people around have a system like yours and those that do wouldn't try to run it with an Ultra PSU. Go with the Corsair, it should be available very soon.
  3. Yeah. This was fine to run one card on and I realized that it probably isnt a good idea to push my luck with two.

    I think the corsair 1000 watt or the enermax blood raven suggested would be more than ample power supply for a time to come.

    Im not going to install my second card until I get a high end PSU for that very reason. I was in hopes that 450 watt juice box would have been enough to power the second card but wasnt.

    As the EVGA tech stated theres no substitute for a good PSU and Im convinced.

    Thanks for the input guys...
  4. 1000 watts for 3 8800gtx is definatly overkill, im using a rocketfish 700 watt, i have 2 gtx 260s in sli mode with a quad core amd 9950 oced to 3.4 stable 8gb ddr2 1066 ocz and a 128gb ssd and a 300 gb 10000 rpm hard drive and i get no stutter and i run stability tests all the time and get no problems with it running 24 hours at full capacity
  5. I'm kind of in the same boat. When I built my machine, I wasn't thinking of sli or adding more hardware. I'm regretting not spending more on my PSU.
    I had 1 9800gtx, 1 HD, 1 DVD, 5 fans and a Q9450 that I ran stock. All running on a 700watt psu.

    Now i've OC the Q9540 to 3.4 from 2.66, running 4 HD's 2 of which are in raid 0, 2 DVD-Roms (which usually burn at the same time), 2 cold cathodes, 6 fans and two more 9800gtx's are in the mail.

    The only option i've got for a psu that can handle this is the Enermax Galaxy EVO 1250watt. And that's only due to the fact that the 1000watt is completly sold out everywhere in town. But for the extra $20, 250watts is a steal. It'll still be $350.
    I agree with ausch30, there's no such thing as overkill when it comes to your psu. In the end, it'll be the most important part of your computer's future.
  6. Since you mentioned the lack of availability, where in the world are you?
  7. Alberta, Canada.

    After reading a few forums and reviews, I picked up the Corsair HX 1000W. Haven't installed it yet, but when my cards show up next week, it'll be fun to install everything. Cant wait.
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