You can only use the video outputs from the master SLI. And you will also need an NVLink bridge for the 2000 series.

NVLink 

Your reply suggests that I am in SLI.

I am not in SLI. So if I’m in SLI with a bridge I can only use outputs from the primary card. 
What about not having a bridge and not being in SLI? 
is this more of a question for Nvidia? 

It's unclear what you want to do with the 2 video cards. 

I am assuming you do not want to run them in SLI. So without the bridge they will be running as 2 independent cards.

Windows only supports monitor output from both cards in desktop mode (2D). Windows also has the option to send a workload to 1 card or another, but not the same workload on both at the same time.

Any 3D workload will only use 1 card. To use both cards in a 3D workload under windows requires SLI mode. In SLI you can only use the video outputs from the master card.

Wow, cool setup (leaving aside resolution quality over projectors).

As for dual GPU in different slots - since those are bound to different bus lines (upper 16x PCIe Gen3 slot is CPU-bound, lower x16 is hooked directly into PCH) without SLI it would have to transfer quite a lot of data over DMI 3.0 (it has a bandwidth of a bit below 4GB/s for 300 series chipsets {x4 lanes} and 8GB/s for 500 series chipsets {x8 lanes}) - same DMI is used for other purposes (e.g. Storage to CPU, peripheral devices, etc.) resulting in a significantly degraded performance.

I am not in SLI What I want to do is use the outputs from both cards. 1 card for gauges and the Garmin GPS which take very little computing power and video card power. The other card is for the main graphics of the flight sim which wound be in Nvidia surround mode, all 2D.

You would have to divide the load to each card by manually selecting which card you want what load on. If If is all 1 software package that will likely not work unless multiple card selection is incorporated in their software.

No idea if that flight sim supports that or not. That would be a question to ask in their forums.

---

@sogibm wrote:

I am not in SLI What I want to do is use the outputs from both cards. 1 card for gauges and the Garmin GPS which take very little computing power and video card power. The other card is for the main graphics of the flight sim which wound be in Nvidia surround mode, all 2D.

---

I'm trying to imagine how this works. On my Windows systems, I've always had at least 2-3 monitors connected. 

I also have a nice gaming/Kodi computer in my Home Theater that I use on our Epson 1080p projector and it works fine and looks great. We have a plasma-TV in there as well, but it's output is just a clone with a HDMI-Splitter. Everything runs thru my Onkyo-AVR.

So, yeah ... having the video-cards drive all those projectors and monitors is more important than SLI. So, sounds like your hardware is connected correctly. Everything else you do with software.

Even though Direct-X games are usually played on a single (now-days large) monitor, I have some games that allow you to display or target certain screens/elements to 2nd or 3rd display-monitors. This happens because the developers made a provision for it. One that come to mind is FarSight Studio's Pinball Arcade. They allow you to display the Back-Glass/Score on the 2nd monitor.

Finally, you are not the first to want to do this with a Flight-Sim. I'm sure they guys/gals in one of the more popular flight-sim forums could help you with configuration of your software to help obtain your objective.

Nvidia does make cards that support 8 monitors, but they are for professional use and not cheap...

NVS 810 

Yes, they do, but NVS aren't designed to be high-performance GPUs, this line is more for video-marketing purposes (e.g. public areas, shop advertisement displays).

For 3D operations and multiple displays Quadro professional line are more suitable, but those aren't optimized for gaming (therefore does not meet TS' request, who's configuration rather looks like pilot training equipment).

Microsoft clearly outlines GPU recommendation listing gaming class cards there on a first place.

I know, but if you look at the posting:

"1 card for gauges and the Garmin GPS which take very little computing power and video card power. The other card is for the main graphics of the flight sim which wound be in Nvidia surround mode, all 2D."

Looks like this is maybe a custom flight simulator or something like that. I have never seen a 2D flight sim, they are normally all 3D.