Tesla gaming (and more)

[test]

What is the most proper way to re-route output from a rendering card 
(which can have it's output disconnected or don't have it at all) to a 
displaying card (weak one, iGPU etc)?
For example, a laptop with an external card in an ExpressCard riser (no 
external display is connected to the card), or a desktop PC with 
embedded video plus Nvidia Tesla?
How should I configure Mesa in order to get «auto-screen-grabbing» from 
the rendering card to the displaying one?