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For my birthday, I just got a 3rd monitor. Instead of replacing the smaller of my two monitors, I'd like to just use all three.

I currently have an Nvidia GTX 275 with 2 outputs, so I know I'll need another video card. Do I have to buy another GTX 275 card to get SLI to work or to use the 3 monitors? Or can I go to the computer store and buy a $50 video card and use that?

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4 Answers 4

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Happy Birthday!

If you are using Windows Vista, the video subsystem only allows drivers from one company e.g. Nvidia, ATI, Nvidia etc.

Therefore, you should be able to get this working with any second Nvidia card.

SLI however is dependent on another video card in the same series, so if you get a $50 card, do not set it as primary (If you motherboard has one slower SLI slot, put it in the slower slot).

If you are using Windows 7, you should be able to have a secondary card of any manufacturer (that being said, I still prefer to keep it within the same company!).

To sum up - using a different card will achieve what you want without problems, however use as secondary otherwise performance may go down hill.

If you have any other outputs such as VGA or HDMI, you may want to try and get an adapter to power all from the first card.

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If you have Vista you have to buy a card that uses the same driver as the first card.

Win 7 allows you to have multiple drivers for multiple video cards.

I'm not sure but I think you have to have identical cards to run SLi. Additionally, I believe that you can only run SLi on one of the monitors with the latest drivers from Nvidia - and even then I think that only works with two monitors. I have no idea if it can even deal with three monitors.

I have dual 8600M GT cards on my Toshiba X205-SLi1 and it was until recently that they even let you run SLI with dual monitors - even then you had to select which monitor was the primary.

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SLI can only be enabled if you have one logical monitor in Windows. This means when you go to Display Properties, you see only one monitor there. Now, you can have multiple physical monitors that map to one logical monitor, but I personally don't like that - When you maximize programs they maximize across all montiors, taskbar goes across all monitors, etc*.

SLI works easiest when the video cards are identical - there are ways around this, but I'm not sure of them. You do need to install a cable between the video cards. It will obviously need to be an nVidia card.

*There are 3rd party programs that can somewhat alter this behavior but it's not 'in' Windows - they're other programs.

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Buy another card and put it in SLI has some requirements:

  1. You are motherboard has to accept SLI configuration
  2. You are power supply has to afford the extra power

In you particular case I would suggest you to think to replace your NVIDIA 275 with the newest ATI 5000 series, that supports by default 3 monitors.

You could buy the 5750 or even 5850.

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