How to replace igpu with dgpu

Hello; i have a main gpu with hdmi out a nvidia Black gtx 6 gb and i have a nvidia tesla m40 with24 gb and no hdmi ports.

Só basicly i need nvidia prime to get the tesla offloading thru the titan.

Prime-run does that but with a huge fps drop.

A couple of times i was able to put the m40 as the main gpu while using the hdmi out of the nvidia titan

But i cant replicate it and im not sure wich manual is Best anymore.

Do you guys know how to do this?

Best regards Carlos

I suspect a new cable or an adapter would be easier and work better.