When selecting Extended desktop mode in Windows screen configuration menu, you can also choose to 'Disconnect' a display. Doing this for all the NVS810 outputs then made the GTX available as a renderer for Resolume. Then we could reconnect the NVS outputs again, while Resolume continued to run on the GTX.
Officially, we only support running Resolume on a single GPU. We can guarantee Resolume will work with every output on a single GPU. If it doesn't, you can contact us. If your problem requires a technical fix from our side, we will make that happen.
Using multiple GPUs usually is fine. Using the two D600s in a MacPro works without problems, just like two GTX series cards together. But it's not officially supported. This means we cannot guarantee a two GPU setup will work for you, and we cannot commit to a fix if it doesn't. Of course, we'll give as much advice as we can, and the forum is also always very helpful. But if it really doesn't work for you, there's nothing we can do about it.
This is not meant to discourage you, I just want to be sure there are no misunderstandings