Breaking the SLI "Code"

With the flood of nForce4 motherboards getting ready to enter the market, we had a decent selection of very recent nForce4 Ultra and nForce4 SLI motherboards. We also had both the SLI and the Ultra versions of the DFI based on the same PCB. With this wide selection of boards, we could look at the differences in the Ultra and SLI chipset and also confirm that they were not unique in any way.

If you look closely at the pictures of the SLI and Ultra, you will see that the chipset themselves appear identical. However, a closer look at the resistors and pads surrounding the chip shows some differences. The resistors appear the same on both, but there are 3 sets of resistor pads that are closed on the SLI chipset while just two sets are closed on Ultra. The vertical set of resistor pads just to the right edge of the chip itself is closed on SLI and open on Ultra. We could find no other obvious differences in the 2 chipsets. Could it be this simple?

We closed the set of resistor pads on the DFI LANParty UT nF4 Ultra-D with conductive paint, as you can see in the photo below.

We set the jumpers to SLI, attached the top bridge from an SLI board, since the Ultra boards do not ship with an SLI bridge, and fired up the system. The system was immediately recognized as an SLI chipset on boot and in Windows XP by our latest 71.40 Forceware drivers. Our little bit of very easy modification had "turned" the Ultra chipset into SLI. We no longer had driver limitations and performance was now exactly the same as the performance that we achieved with a normal SLI chipset.

We also tried modifying an Ultra to SLI with an ordinary #2 pencil. It worked perfectly, and with there being so much room around the set of resistor pads, you don't have to be that neat. If you close the pads, you have converted the Ultra to SLI. Those of you who remember Athlon XP modding for CPU speed will recall how close the sets of pads were in that mod. This required masking and careful painting of the pads to be closed. With the Ultra to SLI mod, there is huge real estate around the resistor on which you are working. As a result, even "all thumbs" modders should have an easy time with this one.

Index Performance: x16 vs. x16/x2 vs. x8/x8 (SLI)
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  • Wesley Fink - Tuesday, January 18, 2005 - link

    #40 and #44 -
    When the pads are closed on the nF4 Ultra chipset the chipset is then identified as SLI by the system and OS and performs the same as SLI. The x8/x8 is the nVidia defined SLI mode that works after the mod. The board can also - in addition - perform in x16/x2 mode.
  • icarus4586 - Tuesday, January 18, 2005 - link

    When the Ultra is modded to by closing the resistor pads, can it function in 8x/8x mode? At some points in this review I wasn't sure whether the modification allowed 8x/8x or just 16x/2x. Will 8x/8x work on a modified Ultra motherboard, as long as (like DFI's) it has 2 full length slots?
  • KristopherKubicki - Tuesday, January 18, 2005 - link

    Googer: Wesley is correct. The MSI "DBS" board had an open ended 4 lane slot with a full 16 lane slot. The DFI board runs on two 2 lane slots.

  • archcommus87 - Tuesday, January 18, 2005 - link

    Does even a simple pencil mod like this void any warranty on any board?
  • Cygni - Tuesday, January 18, 2005 - link

    I honestly dont really see the point of the Ultra to SLI conversion. You are now paying an extra $400+ dollars for the second video card for 50% over the performance of one video card... it doesnt make sense. The 8x/8x SLI made the performance for the expendature much more attractive.

    The whole process of changing the Ultra to SLI is very cool, however, haha. Personally, I still see the extra $100 for a true SLI as worth it when you are already shelling out $800 for video cards (assuming 6800U's).
  • Zebo - Tuesday, January 18, 2005 - link

    I just don't see the attraction. It's slower obviously and anyone doing sli can afford a non-hacked solution like real live sli.

    Right now you can get SLI boards for $200. Thats insignifigant premium compared to two GT's @$500 a each. And especially after this flood of new boards price will come down on the real sli boards.

  • bob661 - Tuesday, January 18, 2005 - link

    I said "cheaper" not cheap. Maybe you need to bone up on your reading comprehension skills.
  • Crassus - Tuesday, January 18, 2005 - link

    Wesley, thank you for following up on my comment.
  • Googer - Tuesday, January 18, 2005 - link

    By the way SLI offers a poor price to performance ratio, IN some games the performance is 10-15% or less and in others there is none. A single 6800ultra
    can beat a 6600 sli setup in MOST games.
  • Googer - Tuesday, January 18, 2005 - link

    Wesley are you sure it was MSI that had the x4 slot and an sli mode for the nFORCE4 ultra, because that discriptrion sounds more like DFI than any MSI beta board that I have seen lately.

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