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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  • Klaasman - Tuesday, January 18, 2005 - link

    What would be sweet is TWO Gigabyte 3D1 for a total of four GPU's.
  • mclearn - Tuesday, January 18, 2005 - link

    Are there any visible differences in the DFI Ultra and SLI boards? Maybe the fix for this is as simple as the chipset's "upgrade"
  • Deucer - Tuesday, January 18, 2005 - link

  • cnq - Tuesday, January 18, 2005 - link

    Nice article, and thanks for switching your SLI measurements to 12x10 & 16x12 (I savaged you for including 10x7 in a prev review, which probably no SLI user will both with).

    One suggestion for future FarCry runs on SLI: please try with the magnificent eye candy setting "HDR" enabled (new with FC v1.3). It looks great, but is a graphics card crippler -- and thus the **perfect** test for a 2x6800U SLI system.
  • Wesley Fink - Tuesday, January 18, 2005 - link

    Unfortunately the Gigabyte 3D1 dual-gpu 6600GT does NOT work on the DFI when trhe jumpers are switched to SLI mode. The nVidia driver sees that the system is SLI-capble, but it does not recognize the 2nd GPU as there for SLI. This is true with 66.93, 70.90 and 71.40 drivers. If the Gigabyte single-slot dual-GPU would work with more boards they would sell a lot more of them.

    However, the Gigabyte 3D1 in x16/x2 mode performs quite well when jumpers are left in normal mode. After the mod to SLI it works fine with drivers to 70.xx.
  • crazyeddie - Tuesday, January 18, 2005 - link

    It would be a little late in the game for Nvidia to go back and do a whole lot of reverse engineering to the NF4 SLI chipset to make it less moddable (new word?). Nvidia will:

    A) Let the NF4 Ultra out the door as is, eat the lost sales of more profitable SLI chipsets, and take solice that their graphic card sales will be quite brisk. This presumes they can actually ship enough video chips to take advantage of the increased demand.

    B) Dry up the current supply of Ultra chipsets and go back to the drawing board to disable them more thoroughly. They will miss out on shipping Ultra chipsets to motherboard manufacturers, which may or may not cause contract problems. It would ensure the continued desirability of the SLI chipset at higher margins, however.

    I've personally been hoping for an inexpensive PCI-E board for the 939 Athlon 64 platform that I can pair with a Radeon X800XL solution. This news story jeapordizes the shipment of the NF4 Ultra if Nvidia is determined to protect margins for the sake of overall volume. I guess it's no loss to me, because I couldn't buy an X800XL right now anyway.

    I guess we'll have to wait and see whether Nvidia wants to focus on volume or margin-per-unit.
  • Wesley Fink - Tuesday, January 18, 2005 - link

    #22 - Your idea was so intriguing I had to give it a try. With the DFI UT Ultra modded to SLI, jumpers in normal (non-SLI) position and the Gigabyte 2 gpu 3D1 I was able to run SLI fine with drivers up to 70.xx. This suggests that the Gigabyte Dual 6600GT might run in the single slot of any nF4 Ultra motherboard in a "semi-SLI" mode. That means 2 video cards are potentially NOT required. Modding to SLI woujld enable a wider range of working drivers. More testing needs to be done before reaching any conclusions.

    I am getting ready to try the Gigabyte 3D1 now in full SLI (x8/x8) mode to see if that works on the DFI.
  • ChiefNutz - Tuesday, January 18, 2005 - link

    #23, #27 I dunno, when you go to the DFI website, it shows a picture with the link in the box contents on the ultra for the box contents, and
    for the main product page. It's sitting right there in 3 of the 4 pictures right below the Package listing? What gives?
  • adnauseam - Tuesday, January 18, 2005 - link

    the one I think everyone is missing is....where do you get a SLI bridge, without purchasing an actual SLI board. Remember the bridges ship with the boards not the cards, because the spacing between the PCIe slots could be different on each maufacturers board. It seems the only way to get one would be to wait until someone who doesnt plan on using it sells one on ebay. unless........there is a way to purchase a replacement....Ill have to check that out actually.............
  • razor2025 - Tuesday, January 18, 2005 - link

    This is awesome find. It gives us more choices. I was planning to buy a NF4 board, so I can use the X800XL I have in pre-order. I didn't want a SLI-ready setup, because the cost is too much. However, if I can get a SLI-capable board (after hack) like the DFI UT for around $130-140, I'll definitely go for them. Most single SLI NF4 boards are fetching around $130-140, and if DFI UT and the Epox board retails for around the same price, everyone who wanted a single SLI NF4 will changed their decision to these awesome boards. Even though I won't be doing SLI anytime soon, I'm sure there will be capable and cheaper cards that can run SLI on these boards down the road. If that doesn't happen, oh well, I still needed a PCI-E board that use Athlon64.

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