Check out AT's update to their DFI MB review which, in part, referred to the DFI Ultra-D's convertability to SLI functionality: Here's the relevant quote:
"UPDATE 2/05/2005: nVidia has acted to prevent, or at least make it more difficult, to mod the Ultra board to SLI. First, DFI has advised us, and posted on their website, that they will NOT sell the SLI bridge to buyers of the Ultra board. Second, nVidia has advised us that future shipments of the Ultra chipset have been modified so that the mod to SLI will no longer be possible. An additional side effect of this second action is that the "Dual Video" mode, which performs at about 90% of SLI performance levels, will only work with nVidia SLI drivers 66.75 or earlier. If you do a quick check of web driver postings you will see it is now very difficult to find 66.75 drivers. With a chipset modded to SLI the "Dual Video" mode worked through 70.xx versions of the nVidia driver. nVidia also made it clear they will continue to make driver changes to prevent functioning of any "non-standard" (8X/8X) operation of their SLI driver. This also throws into question whether the VIA "dual graphics" mode on the 894 Pro chipset will ever work with nVidia graphics cards. If you are interested in the current UT Ultra-D we suggest you buy one now if you can find it. Future versions of the UT Ultra-D will not have the same capabilities as a result of these actions."
I'm sure that Nvidia's release yesterday of updated NF4 drivers was not a coincidence. It was noted that Nvidia was violating their own UDA policy in doing so. And although these drivers will (hopefully) fix some of the problems experienced with NF4 MBs, sounds like Nvidia had an ulterior motive.