If you have been following the news, some very strange things are going on with the nVidia nForce4 chipsets. About six weeks ago, MSI showed an nForce4 ULTRA motherboard with a regular x16 PCIe slot, plus an open-ended x4 PCIe slot. Those who saw the demos said that MSI was running two matched video cards in what they called a "semi-SLI mode", which ran at about 90% of the performance of normal nVidia SLI. This was an interesting development because nF4 Ultra chipsets are cheaper than nF4 SLI chipsets. The boards based on the Ultra chipset are, therefore, much cheaper than the high-end SLI parts that we are seeing in the market. An arrangement like this would be a god-send for computer enthusiasts who watch their budget, yet still like to enjoy most of the benefits of SLI dual video-card performance.

Just as quickly, we learned that nVidia was not happy with this "SLI hack" and they changed their drivers quickly so that "semi-SLI would not work with current and later Forceware drivers." It appears that the later Forceware drivers check the chipset ID and if the driver sees "Ultra", then SLI is not enabled. MSI decided to kill the "semi-SLI" board because it would be a nightmare supporting a board that would only run with older nVidia SLI drivers.

Then, at CES, DFI was displaying both nForce4 SLI and nForce4 Ultra motherboards with two x16 PCIe slots. We were told that Epox also had an nForce4 Ultra motherboard with another semi-SLI solution based on the cheaper Ultra chipset. DFI told us that they used the same PCB for both versions of the nForce4 boards for economy, and that in fact, the nForce4 Ultra board could run a dual x2 video mode with earlier nVidia Forceware drivers in addition to standard single x16 video mode. Given AnandTech's close working relationship with DFI, we had arranged an exclusive look at both DFI boards. When the boards arrived, we were indeed able to run an x16/x2 dual video mode on the nForce4 Ultra with driver version 66.75 - a very early nVidia SLI driver. We tried many, many Forceware versions and also found that 70.41 also worked by adding one line to the registry. However, like MSI, the Ultra dual-video only worked on very old SLI drivers or on drivers with a Registry mod.

It was clear at this point that this Ultra dual-video solution did work, but that nVidia had turned it off in recent drivers. This caused us to wonder what was really going on with nForce4 chipsets. If nVidia could enable/disable this Ultra SLI in drivers, then the base chips must be very, very similar. In fact, it would be logical if the nF4 Ultra and nF4 SLI were exactly the same chip with some modification, making the chip an Ultra in one case and an SLI in another. The pin-out configurations are, after all, exactly the same with both chipsets.

It was with this idea that we took a closer look into the possibilities, and what we found will surprise you! It turns out that the nForce4 Ultra is apparently just an nForce4 SLI with SLI turned off. What is even more important is that we also found a way to turn on the disabled SLI!

Breaking the SLI "Code"


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  • Dmitheon - Tuesday, January 18, 2005 - link

    Kudos to Wesley and the rest of Anandtech for finding this neat little hack. I wish nVidia simply didn't have the Ultra line of boards, and let the economy of scale bring the SLI board down. I'd love to see the amount of money that went into taking SLI down a notch so they could market a less expensive chipset that costs nearly the same to produce. Personally, I'll end up buying an SLI board as more hit the market and competition brings the price down from it's current $190s (just checked Why spend extra? The piece of mind that comes from knowing that nVidia is not trying to take a feature I want, away from me. To paraphrase a hookey old public service announcement: "SLi, it's not a right, it's a privledge" ;) Reply
  • bersl2 - Tuesday, January 18, 2005 - link

    I'd rather that more nforce4 boards actually *get* to retail in the first place. Some of us don't want an SLI board (yet)... Reply
  • Jahara - Tuesday, January 18, 2005 - link

    I'm confused. Doesn't the SLI crossover chip only come with SLI enabled motherboards? Reply
  • Crassus - Tuesday, January 18, 2005 - link

    Does that mean that you could use any Ultra-mainboard with only one PCIe slot and run the Gigabyte 2-chip-6600GT in there with that mod? Reply
  • Neo_Geo - Tuesday, January 18, 2005 - link

    Yep, reminds me of the GeForce/Quadro hacking possibilities.

    Hopefully, nvidia will just eventually merge the Ultra and SLI into one product.

    In the case of the GeForce/Quadro, they came out with some updated drivers to discourage hacking. Then, when that was figured out, they went a little deeper and physically changed the cores. Now, a software hack is not totally possible on GeForce (I say not totally, because the hack does partially work and gives a geforce most quadro features, but not all).
  • Wesley Fink - Tuesday, January 18, 2005 - link

    #16 -
    The DFI LANParty UT (Ultra chipset) will sell for about $140 and it can be modded to SLI. The full DFI SLI-DR will sell for about $200. There are Ultra chipset boards that sell for even less than $140, but we don't know yet if they can work as modded SLI yet - and most don't have dual video slots. There are also some very high end SLI baords that sell in the $250 to $300 range.
  • PetesEscapade - Tuesday, January 18, 2005 - link

    Helps to put something in.....

    I love it. Regardless of nVIDIA's motives, or lack thereof, it is great to see people digging, tweaking, and passing the info along to the rest of us to do with what we will.


    Why did man climb Mount Everest? Because it's there. Why try to turn a nForce4 Ultra into a nForce4 SLI? Because it's there!
  • PetesEscapade - Tuesday, January 18, 2005 - link

  • bupkus - Tuesday, January 18, 2005 - link

    Of course ATI is rushing SLI solution video cards for the nForce4 SLI and now Ultra chipsets. My guess would be their drivers will attempt to exploit the Ultra hack, unless legal advises not. nVidia understanding this and seeing their dilemma of more chipsets vs. more video cards will choose both and rush an nForce4 Ultra version 1.1. If not, ATI's SLIs will force nVidia to allow the hack in their drivers. Could an ATI chipset with a cheaper ATI SLI design open the door for ATI's chipsets?
    Hehe, lets wait and see.
  • skunkbuster - Tuesday, January 18, 2005 - link

    i wouldn't call $229 cheap. still pretty expensive to me


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