Multiple Simultaneous Rendering Unity Instances

I already figured out that you can launch multiple instances of your Unity application.
This works very well!

Unfortunately, only one of these instances is rendering at a time. The others seem to pause if they lose focus. However, I need all of them to be active and rendering all the time.

How/Is this possible?

Or would that need source code access to the Engine?

You can use Application.runInBackground = true; to make your process run even when it lose focus.

You might also be interested in the following links when running multiple instances.

The orginal post here:

http://forum.unity3d.com/threads/use-of-multiple-video-cards-running-multiple-instances-of-a-unity-standalone-player-on-windows.382751/

Turns out that (from unity 5.2), you can use a command-line flag (ā€œ-gpu 0ā€) to have each instance render on a separate/dedicated GPU.