The complete idiots guide to configuring SLI

UPDATE: 11-29-06

I completely forgot about this thread until it was recently bumped. This guide is pretty much worthless now as many of the limitations of early SLI drivers have been worked out. You still need the same chipset on both cards (eg: two 7900gt's) but newer drivers do not require identical drivers and in some cases you can get away with using cards from different manufacturers as long as they are based on the same GPU. Also enabling and disabling SLI no longer requires a reboot as of Forceware 80.00

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Greetings to all you Alienwareites. For those of you who will be upgrading to SLI yourself, you will likely find this guide useful. Enabling SLI can be as simple as checking a box in the NVIDIA properties. But under some circumstances, it can be a real pain in the ass to get it to work right. Lets start off with the SLI requirements:

1. An SLI capable motherboard (duh)
2. Two identical video cards
3. An SLI Bridge
4. An SLI certified Driver set (66.93 or 71.89)
5. Both video cards must have the exact same BIOS


Number five is very important. If you purchase the video cards at different times, both cards will likely have a different BIOS revision on them. In this case we will have to perform the "pain in the ass" procedure.

Ok, now that that is out of the way, let's get down to the nitty gritty. The hardware portion of the setup will vary depending on your motherboard but it basically involves setting the motherboard into "SLI mode" installing the video cards and connecting the SLI bridge. If you have an Asus A8N-SLI you will have to change the selector card so the "dual video cards" side is pointing towards the slot.

Once you get everything hooked up, boot into Windows like normal. Windows should detect the second video card and install it. Now open up the NVIDIA display properties and select the SLI multi-GPU tab. If you are lucky, all you will have to do is check the box that says "Enable SLI multi-GPU." If you see the following screen, we get to perform the pain in the ass method.


Before we get down to it, we are going to need to download some files. You will also need two floppy disks handy for this. First download the following files:

1. boot622.exe (1,030 kb)
2. NVFLASH.zip (177 kb)
3. csdpmi5b.zip (48 kb)

The first file will format a floppy as a Dos 6.22 boot disk. Run the file and insert the first disk. Extract the contents of the other files onto the second floppy disk. Next you have a couple of choices for the BIOS. You can check the website of the video card manufacturer and download the latest BIOS. If the manufacturer does not provide BIOS images (like XFX), you will have to flash the second card with the BIOS from the first card. If you download the BIOS, put it on the second disk.

Before I continue any further, I should throw out a disclaimer. Although I have made this guide as dummy proof as possible, there is always a risk of something going wrong. As such, if you decide to continue from this point on, keep the following in mind: Flashing the BIOS of a video card is done at your own risk. If something does go wrong, don't blame me. If something does go wrong, you should be able to recover by booting with another video card (pci for example) and attempt to re-flash. I would strongly recommend completely reading through this guide before attempting. It would also be helpful to print out the guide so you have all of the DOS commands handy.

Now we are ready to get down and dirty. Boot the computer from the first floppy disk to get to a command prompt and then switch to the second floppy. When you run a command with NVFLASH, you will see a csdpmi.swp error. It is safe to ignore this error. First thing we should do is get NVFLSH to list the video cards in the system.

In the output above, <0> refers to the card in the primary PCIe x16 slot and <1> refers to the card in the secondary PCIe x16 slot. I am not sure what the numbers in the parentheses represent, but if they are different, NVFLASH will complain when you try to flash the card(s). Now let's look at the BIOS information for each card.

In the example above, --index=0 tells the program we are working with the primary card. From the output we can see the BIOS version is 5.43.02.23.04.
Now, lets look at the second card.

If you are going to be using a BIOS that is already on the videocard, make note of which card has the newest BIOS revision. In this case the secondary card <1> has the newer revision (5.43.02.57.00). Next, we are going to back up the BIOS on both video cards.

We gave the backup the name of old0.rom so that we could easily identify it as being from the primary card. Now, backup the BIOS of the second videocard

Now that we have both cards backed up, we are ready to flash. If you downloaded a BIOS off of the internet, you will need to flash both cards. If you are using a BIOS from one of the cards, you will only need to flash one card. In my case, I will be flashing old1.rom to the primary card <0>. If you will be using a BIOS off of the internet, replace old1.rom with the name of the file in the example below.

The switches -4 -5 -6 tell NVFLASH to disregard any mismatch errors between the BIOS and the card. This is necessary for the flash to work. You will be eventually be prompted to confirm the flash.

After entering y, the card will be flashed and you will get a completion message. If you need to flash the second card, all you have to do is change the index number.

Once you have completed the flashing process, reboot the computer into Windows. Once Windows loads, you will see a balloon stating that SLI can be enabled.


Once again, we will open the NVIDIA properties and now we can check the Enable SLI multi-GPU box.


After clicking OK, you will be required to reboot for SLI to become enabled. Click on restart and Windows will reboot.


After Windows reboots, you will see one final balloon stating that SLI is now enabled.


There is one more thing that needs to be mentioned about SLI. While SLI is enabled (via the driver) you will only be able to use one Display. That's right, even though you can have up to four display outputs on your videocards, you can only use one of them while SLI is enabled. If you disable SLI (via the driver) and run the cards normally, you can power up to four displays. But you will have to reboot every time you want to enable or disable SLI. Hopefully a future driver release will leave SLI disabled until you launch a game so you can run multiple displays except for gaming.

And now for some benchmark goodness:

3Dmark 03
Single - 8053
Sli - 13625

3Dmark 05
Single - 3250
SLI - 6235


Well that about does it. If you have any questions or comments, feel free to PM me or respond to the thread.

Well considering THG's latest videocard roundup has the 6600SLI @ 5704 and the x850 @ 6072, I think I am doing pretty good @ 6235 stock.

Finally got around to overclocking my system. Stock for the videocard is 500/1000, I am running 575/1200. Processor is overclocked currently to 2.4. If I bump the multiplier back to 11 I can get 2.6, but I have not tested it yet. Current 3dMark05 score is 7023.

It should not be if you get the cards at the same time, but I saw a post from a fellow forum member who ran into this issue on a new Aurora because of BIOS issues.

The new drivers are less touchy about the cards. I think with the latest drivers you can even use cards from different manufacturers as long as it is the same GPU. EG; You cant SLI a 6600gt and a 6800gt. Also the new drivers do not require a bridge, but there will be a drop in performance if you dont use it.

????