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"


View All Comments

  • Fluff - Tuesday, January 18, 2005 - link

    Pencil trick to make a Quadro 4000 i would like to see!!! Reply
  • cosmotic - Tuesday, January 18, 2005 - link

    (oh wait) Reply
  • cosmotic - Tuesday, January 18, 2005 - link

    Nice comment Dranzerk! Reply
  • Fluff - Tuesday, January 18, 2005 - link

    Oh come on guys. This sort of thing is nice to know. But would you seriously splash out on 2 graphics cards and scrimp on the motherboard?

  • Dranzerk - Tuesday, January 18, 2005 - link

    Our Take forgot to add...

    Getting SLI at anytime counts are you being a moron for spending so much money regardless of a mod that saves you a few bucks. SLI = Worst nvidia ploy ever.

    I mean come on nvidia, think up something original than what everyone else has did.

  • Filibuster - Tuesday, January 18, 2005 - link

    This reminds me of the Promise Ultra100 to Fasttrak100 mod.

    "Nvidia.... that greedy money hogging .... trying to milk us customers for all our worth."
    Lol...they _are_ a semiconductor company, what did you expext? Last I noticed none of these guys are not for profit agencies...the fun is in outsmarting them (unlock and overclock, unlocking pipelines, turning on sli).
  • Wesley Fink - Tuesday, January 18, 2005 - link

    ALL -
    We apologize for the posting confusion with this article. It was scheduled to go live this morning, but was accidentally auto-posted around midnight by our document engine. We immediately pulled it down and posted this morning as originally planned. That is why some of the comments have odd times for a 7:30AM post.

    We think you will find the information worth waiting for.
  • PseudoKnight - Tuesday, January 18, 2005 - link

    Don't get me wrong. I think this was great investigative work. I just hope it proves fruitful at the retail level. Reply
  • Jii - Tuesday, January 18, 2005 - link

    I knew something like this had to be lurking underneath and here we were again.

    It's great to see that there are people who have the time and imagination to start even looking this opportunity and bring this to public.

    The only drawback is that now Nvidia knows that we know the thing, that they didn't want us to know, that we now know (you know) ;-).

    But seriously: As the modding possibility came to public view, my best guess is that Nvidia will, instead of tweaking their drivers, start modifying the chip structure in a way, that such modifications will become harder to accomplish, completely impossible or will make no difference.
  • Aquila76 - Tuesday, January 18, 2005 - link

    >>As you will see in our upcoming reviews, it is also one of the most enthusiast-friendly boards to land on the market since the DFI Socket 754 motherboard.<<

    Do you have an ETA for the nForce4 roundup? I have a $3K tax return coming and am building an Uber-AMD64 SLI dual-Ultra rig and want to know which is the best SLI for the buck.

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