Why would you want to do it. There would really be no reason as you can not get them to run together ie crossfire or sli. Only reason to do this before was physx anda gtx 285 is overkill for that.
You don't understand what he's asking, he's talking about Lucid's Hydra chip that is included on this MSI board, it's supposed to allow you to mix vendors and cards, and it intercepts the driver & API calls and renders from both GPUs.
Google 'Hydra 200' .