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  • SLI help

    I think I have the answer for this but I am just looking for verification so here goes.

    I have just purchased a second EVGA 7800GT pci-e 256mb gfx card to run SLI. Everything seems to be fine but when I plug the second card in and restart the system I can't get it to fire. The system has no juice at all as if the power supply wasn't plugged in at all. I have swapped the cards and it has made no difference. Here is the weird part I have one card plugged in with the 6 pin connector and I have left the other card's 6 pin connector off and the system starts.

    I am assuming that my PSU isn't big enough to handle SLI. My power supply is 500wts Xconnect. I know of others who have used this same PSU with SLI and have had no issues. The only thing I can guess is that I am running a AMD 754 socket chip which I believe is a bit more power hungry than the 939 socket.

    My specs are

    AMD 754 3500+ CPU
    Epox EP-8npa SLI mobo
    2gig 3200 Corsair Twin X mem
    2 EVGA 7800GT
    1 80 gig hdd

    Any help or advice is greatly appreciated.
    sigpic

  • #2
    Re: SLI help

    Have you tried single cards in both of the PCI-E slots already?
    |TG-12th| Sawviper

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    • #3
      Re: SLI help

      Yes I have sqapped both the cards into the number one pci slot and they both worked in that slot
      sigpic

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      • #4
        Re: SLI help

        What about only one card in the number 2 slot?
        |TG-12th| Sawviper

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        • #5
          Re: SLI help

          Haven't tried that will check and rport back thanks
          sigpic

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          • #6
            Re: SLI help

            Do you have to do something in the bios to tell it it has dual cards or a jumper on the motherboard.
            The Old Guy
            kin3
            sigpic


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            • #7
              Re: SLI help

              No not according to the manual. It states I have to avticate the multi GPU but that is windows based and not bios. I have also looked just to make sure.

              After trying to run both cards together I ran across the issue of it changing the time and date on my system. It also changed my boot priority from my main sata drive and it changed it to an IDE HD I have in my computer. That tells me that the system is loosing power to the mobo correct? Which brings me back to the PSU being to small?
              sigpic

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              • #8
                Re: SLI help

                Yeah, it would be PSU related. If both cards work fine in the slots seperatly, then they aren't the problem. I believe you need a 650w power supply for the cards to run properly. There should be plenty of info on SLI requirements on www.nvidia.com, or at least on the internet as to the exact requirements.

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                • #9
                  Re: SLI help

                  Ditto on acid's comment. If you elimiate the GPU being the problem by trying each separately and then elimiate the PCI-E slots being the problem by successfully using either with a single card, then the most likely problem is the PSU. What brand/power do you have anyway?

                  -TF
                  Twisted Firestarter
                  a.k.a |TG| Harkonian
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                  • #10
                    Re: SLI help

                    500 watt xconnect
                    sigpic

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                    • #11
                      Re: SLI help

                      Ultra X-Connect 500W: Only 28A on the 12V rail. SLi will require more than that, I'm afraid.
                      A policy of freedom for the individual is the only truly progressive policy. -F.A. Hayek

                      "$250,000 a year won't get me to Central Park West."

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                      • #12
                        Re: SLI help

                        To run dual 7800GTs, you'll need a PSU with a Dual +12V Rails. A single rail is not sufficient to handle the power requirements of two 7800GTs. Preferrably something with 12A on each rail or higher. Or else you might run into problems later down the road (PSU wearing out early, etc.).
                        |TG-18th| Acreo Aeneas
                        TG World of Tanks Clan Executive Officer
                        Former 9th & 13th

                        Pronounciation: Eh-Cree-Oh Ah-Nay-Ess
                        Still can't say it? Call me Acorn then. -.-





                        SSDs I Own: Kingston HyperX 3K (240 GB), Samsung 840 Pro (256 GB), Samsung 840 EVO (250 GB), Samsung 840 x 2 (120 GB), Plextor M5S (120 GB), OCZ Vertex (30 GB)

                        TG Primer and Rules

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                        • #13
                          Re: SLI help

                          Thanks for all the help much appreciated
                          sigpic

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                          • #14
                            Re: SLI help

                            Yeah you need to step up your wattage drizz. I'm using 600 watts myself, and I think I need more power w/all my peripherals plugged in to boot properly.
                            |TG-33rd|Clawhammer
                            [squadl] [sniper][unit]


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                            • #15
                              Re: SLI help

                              Hey guys just wanted to say thanks for all the help. I got my SLI running tonight. It was the PSU, I bought an Antec 600watt PSU that is SLI ready and things are running great.

                              I just put up a 10166 score on 3DMark05 which is about a 3000 point improvement from my original setup

                              Specs
                              AMD 3500+ 754 socket CPU
                              Epox SLI mobo
                              2 7800GT
                              2 gig Corsair Twin X memory 3200

                              Thanks again to all who helped
                              sigpic

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