GTX970 SLI/ 3x monitor setup

[Dunndunn]

I have 2 GTX970s in SLI already and 3x 1080p monitors on the way. My question is what will I need to have them up and running? cables, drivers, anything else I may be unaware of ? Also in terms of connecting all of them can you connect two plugs to one gpu (hdmi/dvi) and the third to the hdmi or dvi on the second card?

 

[MarkW]

If you are using a 1150 motherboard, 2 cards is your limit with Nvidia cards.

There is one exception. A tiny number of motherboards have whats known as Plex switches on them. To be honest, I have not seen a review that covered such a motherboard in years. But if there are any still shipping, they cost a lot more than the average motherboard, and as long as the video cards are not more than 2 slots wide, they can work.

The reason 2 cards is the limit is that Nvidia requires a minimum of 8 PCIe lanes per card. Intel chips only give you 16 lanes, so when one card is in the CPU slot closest to the CPU, and nothing is in the next 16x slot, the first slot gets all 16 lanes. As soon as a card is also plugged into the second slot, both slots become 8x/8x electronically. So if you were then to plug a third card into the third PCIe 16x slot, the second and third slots would change to 4x each, which would leave you with a 3 card setup of 8x/4x/4x. Again, Nvidia requires 8 lanes per card, so the second, and third cards would be dropped from the SLI, and the first card would be getting 8x, while the other two would sit there idle.

On 2011-v3 motherboards, the CPU's come with 28 or 40 lanes. You have to research how the lanes are handled, as it seems that every motherboard does things a bit different, but with the right width video cards, most of these motherboards can go 3 way SLI. And some can go 4 way if installed in a case that allows for the 4th card as well. I am not saying that doing this is a smart thing to do. I am simply saying that it can be done.

 

[Dunndunn]

I appreciate the reply MarkW but my question is more aimed at the video plugins on the cards. I already have the 2x GTX970s installed and have been running them for a few weeks and I'm not really looking to add a third 970 anytime soon, I was just wondering if when I'm plugging up the 3 screens do I need to plug all 3 into 1 of the GPUs or could I split it up and have my hdmi and dvi plugged into GPU1 and either the hdmi or dvi on the second card?

 

[MarkW]

You need to plug them all into one of the cards, in SLI mode there is a master card that is feeding the screens, the other cards it are hooked to become the slaves and do not attempt to output anything to monitors.

I found an article that goes in depth about doing this that should help you as well.

http://lifehacker.com/how-to-set-up-triple-monitors-for-super-widescreen-gami-1680863770