SLI – The Requirements

There’s been a lot of confusion as to what is required to run a SLI configuration, so we put together a quick list of the things you’ll need:

  • Everything necessary to put together a working system, including SLI motherboard
  • Two graphics cards with identical GPUs from the same manufacturer.  Video BIOS revisions must also be identical. Note that if the cards run at different clock speeds, the driver will run both cards at the lower clock speed of the two.  NVIDIA has announced their SLI certification program, which means that two SLI certified cards should have no problems working in tandem. Currently only NVIDIA cards will work in SLI mode although ATI plans on introducing SLI technology in 2005.
  • A power supply capable of supplying adequate power to the system as well as both graphics cards.  Note: you may need one or two 2 x 4-pin to 1 x 6-pin PCI Express power adapters if you are using two 6800GT or 6800 Ultra graphics card with a power supply that either has no or only one 6-pin PCI Express power connector.
  • A SLI video bridge connector.  This connector should be provided with your nForce4 SLI motherboard. 
  • NVIDIA drivers with SLI support.  Currently the 66.93s are the only NVIDIA sanctioned drivers with SLI support, however NVIDIA is working on rolling in SLI support to all of their drivers, including the newly released 67.02 driver. 

It’s no big surprise that you can’t use different, GPUs; in our tests we tried combining a 6800 Ultra with a 6600GT, but NVIDIA’s driver wouldn’t even let us enable SLI on the combination.  When we tried to combine two different 6600GTs (non SLI certified) we could enable SLI through the driver, but there were tons of stability problems.  Accessing the NVIDIA Control Panel would cause the system to lock up, presumably because the control panel had issues reading from two different video BIOSes.  If we didn’t bother with the NVIDIA Control Panel and just tried to run a game we were met with video corruption issues and lockups.  Right now it seems like the only option for SLI is to have two identical cards; in theory they can be from different manufacturers as long as the video BIOSes and all of the hardware specifications are identical.  In order to make upgrading easier, NVIDIA introduced their SLI certification program which is designed to ensure compatibility between all identical-GPU cards going forward.  Only time will tell whether or not this actually pans out to make upgrading to a SLI configuration easy.

One thing to make sure you have are sufficient power connectors coming off of your power supply.  If you are using two 6600GTs then it’s not a big deal, since the cards themselves don’t require any external power.  However, with two 6800GTs, each card is outfitted with a 6-pin PCI Express power connector, which must be used for proper/stable SLI operation.  Since most power supplies only include one (or no) PCI Express power connectors, chances are that you’ll have to use a 4-pin molex to 6-pin PCI Express power adapter, which takes two regular 4-pin power connectors and combines them into a single 6-pin PCI Express connector.  You should, in theory, use two separate power cables with the adapter (in order to avoid pulling too much current off of a single cable and violating the ATX spec) but in practice we had no issues with using two connectors off of a single cable to power one of the graphics cards.  If you have no PCI Express power connectors on your power supply then you’d need four separate power connectors just to power your graphics cards, add another one for ASUS EZ-PLUG and then you can start thinking about powering up things like your hard drive and DVD drive.  While purchasing a SLI motherboard will pave a nice upgrade path for you in the future, you may need to enable that future by upgrading your power supply as well.

ASUS’ A8N-SLI Deluxe Enabling SLI


View All Comments

  • bob661 - Tuesday, November 23, 2004 - link

    I found one here.
    I don't know if they actually have one in stock though.
  • jshuck3 - Tuesday, November 23, 2004 - link

    Where are they getting the 6800GT PCI Express cards? I can't find them anywhere...are they even out yet or are these just review boards? Reply
  • L1FE - Tuesday, November 23, 2004 - link

    #28 If the nextgen video cards are also SLI capable, then SLI offers even more performance for a new GPU launch. If you don't want SLI that's your choice, but SLI offers consumers a wider range of choices just because cominations now make it that much more complicated. Whether that's a good or bad thing is yet to be seen, but I like how it makes things exciting between new GPU releases. Reply
  • T8000 - Tuesday, November 23, 2004 - link

    Altrough it is nice to see Nvidia take PC gaming quality one step further, these solutions are more expensive than ever before.

    But where does this money come from, you ask. Well, since CPU's are stuck at around 3 Ghz (or almost equal) for some time now, people look for other upgrades to buy.

    And SLI is an easy way to explain that a top-end GPU solution now costs $1000 instead of $500, because it now contains two $500 cards.

    But since SLI is much cheaper than pre-overclocked (Falcon/Alienware) solutions, it is currently worth its premium for a lot of users.

    It also creates an interesting problem for ATI, to sell technology that is way behind for lowewr prices or to copy the SLI concept, hoping that their users are willing to wait.
  • miketheidiot - Tuesday, November 23, 2004 - link

    #28 the next gen of both nVidia and ATI will be only a tiny jump over the current generation. We won't see another big jump until DX10 has been out for a while. The next jump will be a 9700 to 9800 style jump, if that.
  • VIAN - Tuesday, November 23, 2004 - link

    Yeah, where is 8xAA/16xAF. I want that tested. I mean with all that power, who wouldn't want to see the results of the fabulous 8xAA IQ. Reply
  • FICo - Tuesday, November 23, 2004 - link

    So does Nvidia now want everyone to buy 2 of their cards? I really hope its not popular. They should just design faster GPUs rather then relying on such a sledgehammer approach. Nvidia seem to bring out new GPUs once a year, and updates 6 months into a products life. So the new "Geforce 7" chip will be out end of spring time next year. Of course the performance of a single card "GeFroce 7 Ultra" will be a big jump as usual, and will most likely out perform todays PCs with dual 6800 Ultras. Nvidia's SLI technology is certainly interesting, shame its such poor value for money. Surely a dual core approach would be cheaper for the public to buy, yet still offering extra performance. Reply
  • Filibuster - Tuesday, November 23, 2004 - link

    Dual Voodoo2 cards is what, 200Mpixel/s? :) Reply
  • Jeff7181 - Tuesday, November 23, 2004 - link

    Thinking about it more, I think I'd rather just see some 32 pipeline GPU's with 512 MB of RAM and it's very own nuclear reactor to power it :) Reply
  • Souka - Tuesday, November 23, 2004 - link

    Anyone want SLI cheap? don't even have to upgrade your moherboard.....

    For sale.... two 8mb 3dFx Voodoo2 boards wih SLI cable...PCI interface of course..... it rocked in the 90's....why not now?



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