SLI & +12V

Ok so I've had some problems with my SLI setup (two EVGA GTX 570's). When playing Battlefield 3 my game seems very choppy sometimes for having two 570's running it. When I ran a single GTX 570, it ran smooth. I've been searching around the internet and tried many suggestions with no luck. So I finally decided to just call EVGA and ask them what the problem is. The guy that helped me asked about my PSU (which is an OCZ-ZX850W). He said the wattage is fine, but the +12V rail doesn't provide enough Amps for both cards. Each card requires 38 Amps under load, bringing it to a total of 76 total Amps needed. My PSU does a maximum of 70 Amps on the +12V rail.

I guess my question is, will I really see a difference if I get a PSU that has more than 76 Amps on the +12V rail. He also told me it doesn't matter if its a single rail or multiple rails, as long as the overall amps are more than 76.

I've been told this is micro-stuttering, is there a fix? Or did I waste $350 on another GPU? Also, people in other forums asked other questions like my resolution and my other parts. I have a single monitor with 1920x1080 as the resolution. Below are the other parts in my build.

i7-2700K (not overclocked)
Asus P8P67 Pro (rev 3.1)
8Gb Corsair Vengeance
OCZ-ZX850W PSU
OCZ 120Gb Agility 3 SSD
Western Digital 320Gb HDD
x2 EVGA GTX 570 (model: 012-P3-1573-AR)
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  1. I think 2 570s would use 38A under load. They use 2 x 6 pin PCIE connectors from the PSU that can supply max 75W eaxh + 75W from the motherboard = 225W each /12V = 18.75A max each and thats only if they take 100% of the power they possibly can. Do you have issues with any other games?
  2. Nvidia have a list of all certified SLI PSUs
    Link: Nvidia SLI Certified PSUs
    By this link I posted, your OCZ-ZX850W is a certified PSU for 2-way SLI GTX 570.

    So, 4 possible problems:
    - Your other VGA have some problems (try it alone)
    - Your PSU have some problem (don't now how to test it)
    - Yes, it's micro-stuttering... (can't do nothing)
    - You upped too much the graphic settings so your VGAs are running out of memory (try to follow up the memory usage using MSI afterburner and report here the results)
  3. Yeah it is apparent in other games also. I looked up some videos of micro-stuttering and my problem actually seems worse. Way more choppy than what I saw on youtube.


    Don't...
    Bump posts
    http://www.tomshardware.com/forum/283384-33-read-first
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