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I'm doing some research for my next build and I came up across a couple questions that I can't seem to find the answer for on google (I get different answers from each link) So. If I have enough money to get 2 graphics cards and 4 monitors. If I got two SLI Graphics Cards and enabled SLI, would I be able to use four monitors? Or would I be better off getting two different cards and install the drivers for both of them?

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No, you cannot. nVidia cards are limited to driving 2 independent displays per master GPU. When you enable SLI, one GPU becomes a slave to the other, and is no longer capable of driving independent displays.

With SLI disabled, you can power/drive all four monitors just fine.

If you enable SLI however, two will be shut off. You can get one to turn back on if you set the cards to run the monitors in Surround 2D or Surround 3D, but then you lose the benefits of them being separate monitors - windows simply sees the setup as one triple-wide monitor - one independent display (but built off of three linked displays).

There's little reason to get two different cards - If you're not going to run SLI, might as well keep things simple and get two of the same. Then you can always SLI if you need that additional power for something.

What you can do, and I did until one of my cards died, is run 3 graphics cards, two the same, and one different. You can SLI the two similar cards, and use those to power two of the monitors, and then drive the remaining two monitors off of the third card. Because the third card is different & unable to SLI with the first two, it will not have any of its outputs turned off when you enable SLI. It doesn't even have to be an expensive one, unless you plan to run fullscreen applications on the monitors connected to it. I used a $25 card since I only used the monitors for webbrowsing / chat windows or similar, and you can drag windowed games onto the auxiliary monitors and they'll continue to run with SLI since that's all rendered off-screen and composted into place in most of today's operating systems.

You can also look into AMD cards, as they are capable of driving up to 6 displays off of a single GPU (provided correct connectors, usually you'll need a monitor with DisplayPort, or an adapter to convert from DisplayPort to what your monitor can accept), but I'm afraid my knowledge there isn't quite as extensive.

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Don't worry about the lack of AMD knowledge, I prefer nVidia anyways :) –  JavaJosh94 Jun 8 '12 at 19:02
    
This answer is good except there are 3+ monitor nVidia cards that are currently sold. In theory said card would support 3 monitors in SLI. They are of course $400 a piece though. –  Ramhound Jun 8 '12 at 19:35
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AFAIK, the "triple monitor" cards are the GTX295, GTX490, GTX590, and GTX690 - These are all dual-GPU cards, though one of the GPUs is forced to be a slave to the other via on-board SLI. You have to use Surround 2D/3D to power up three outputs as linked displays, and they cannot drive 3 independent displays. If you know a specific model, I would be genuinely interested though - Three independant displays off of a single card is a dream I've had for a long time... @Ramhound –  Darth Android Jun 8 '12 at 19:54
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Yes, you can if you do not use SLI mode. Each card can have 2 monitors (for NVidia), so 2x2 would be 4 monitors.

Although I never tried, @DarthAndroid explains that you cannot if SLI is enabled

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Okay thank you, some of the sites I've looked at (Including nVidias) said that you could only plug monitors into one of the cards which was what got me confused. –  JavaJosh94 Jun 8 '12 at 18:36
    
Though usually, you can only use two of the three (or more) connectors at a time. –  Synetech Jun 8 '12 at 18:40
    
I haven't tried it in SLI mode, but with two video cards total, I have –  Canadian Luke Jun 8 '12 at 18:43
    
I believe he specifically asked if all four would work on two cards in SLI mode, for which the answer is no. –  Darth Android Jun 8 '12 at 18:50
    
@DarthAndroid Edited to clarify –  Canadian Luke Jun 8 '12 at 18:52
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