Either there was an error they wanted to fix, or nvidia threatened legal action. Here is a bit of text from my cache:
"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 also told that Epox also had an nForce4 Ultra motherboard with another semi-SLI solution 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 mode 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 that this hacked Ultra solution did work, but that nVidia had turned it off in 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-outs configuration is, 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!"
...
"In the course of testing, we found that we could actually run the x16/x2 mode on either the SLI board or the Ultra board by leaving the jumpers in normal mode, using an SLI bridge across the two video cards, and enabling SLI in the nVidia driver. Results on the SLI board in x16/x2 mode were, as expected, the same as the nF4 Ultra board or the Ultra after SLI modification. The one huge advantage was that once we had SLI-modded the Ultra chip, we could run x16/x2 mode with any nVidia Forceware driver up to 70.xx. The 70.90 driver was the highest driver to support x16/x2 mode even with an SLI chip, since this would not run with the most recent 71.xx drivers. 71.xx drivers report the board to be SLI-capable, but it does not recognize the second card as an appropriate card for SLI. Clearly, nVidia must have turned off x16/x2 support in the most recent driver as well, only allowing their specified x8/x8 mode to work. We suspect that enthusiasts will find a way to correct this very quickly."
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