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How to get SLI working?

Last response: in Graphics & Displays
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May 8, 2009 12:58:37 AM

Hey guys,

I have a XFX 750a motherboard, and worked with a GTX280 as a GPU for several months. Lately I decided to buy another GTX280 and try to set up a SLI system to improve my gaming performances.

I got the card today and tried to get everything working but to no avail. My windows still seems to think I have only one GPU (even though it made me install software for the SLI bridge when first booted.) I have enabled something in the BIOS for SLI configuration. I tried to follow the instructions on the nvidia homepage about SLI, but the guide says my windows will inform me that the Computer is ready for SLI and to click on the bubble to set SLI configuration. That little SLI info bubble never popped up, only the SLI bridge installation did.

Astra32 seems to detect only one GPU
3Dmark06 detects only one GPU
Vista 64bit only detects one GPU

I have to head out to work soon, so I didn't have time to plug the secondary GTX I received today in single GPU mode (in order to ensure the new card is not a dead).

Can anyone tell me if I am missing an important step in enabling the SLI mode? Are there any problems with Vista Ultimate 64bit and SLI mode? Is my motherboard even more of a piece of crap than I originally thought it was shortly after the install last year? (Don't buy the XFX 750a, I have major USB problems with it and it can only handle 95watt cpu, not indicated anywhere either.)

Please help.

More about : sli working

May 8, 2009 1:59:12 AM

Well, Have you tryed going into >start>control panel>nvidia control pane One of the tabs on the side should be "sli, ect" and it should allow you to enable sli. If you cant see that, make sure your sli bridge isnt upside down, that both graphics cards have power, and that most recent drivers are installed. Are you sure that your new card is working, if none of the above dont work, try switching out your 280 GTX's.
May 8, 2009 2:04:39 AM

All drivers have been installed with the freshest one on the nvidia website
Power is connected, I even have a little green light that turns on close to the DVI connections, it illuminates for both cards

the bridge can be upside down?

and no the nvidia control panel has no SLI options in it because the GPU is not being detected.

I'm gonna try switching the bridge then to see what that gives me, and also I think I saw on some other forums that this mobo has a jumper of some sort of the SLI, but this mobo has no instruction manuals that come with it in the box, so I have no clue where the jumper would be.
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May 8, 2009 12:49:52 PM

Enter your motherboard bios maybe pcie2 is disabled?
May 8, 2009 10:06:24 PM

there were no such options on the motherboard BIOS actually. I did notice I had to change the PCI-E from Gen1 to Gen2 to get the PCI-E 2.0 working, and I changed the BIOS setting to SLI enabled

According to my hardware detecting software (Astra32), I have 1 PCI-Ex16 slot working at x8, and that's it, no secondary.

I'd like to update that I am curently operating with a single card, the one I received by mail a couple of days ago. So it can be confirmed that both cards work.

Also, I have noticed that my mobo takes almost 2mins to start when both cards are plugged, immediately after pressing the power button. After this wait period, the mobo screen shows up, followed by windows. I tried switching my SLI bridge upside down and the same thing happens, though after the windows load bar, windows never shows up and the computer remains idle.

I have opened a XFX support ticket online, I will update you with what they have to say.
May 9, 2009 1:46:50 AM

I'm assuming you uninstalled and reinstalled the video driver after you installed the other card?
May 10, 2009 7:06:13 PM

Ok, here was the problem.

My motherboard had jumpers on it that needed to be moved in order to enable SLI. Combined with the changes in the BIOS, I was able to finally detect the secondary card.

However I found out that my mobo, the XFX 750a SLI, only supports SLI in x8 x8 mode. This gives me a similar performance than a singular GPU running at x16 mode. My 3dMark06 score was shot up from 11400(approx) to 11800(approx).

I was already saving my money to buy a new motherboard and tower, so this disappointment will not remain much longer. But with all my experiences with this motherboard (Bad USB ports, makes bleep noises when started, 95watt only chips capacity, pointless SLI performance, no instruction manual in the box) I am pretty sure that I will never buy another motherboard from XFX again. Their video cards never gave me any trouble though.
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