Parallels on a Mac Pro - GPU question

Curious if a VM can be set up to use a specific GPU on the mac pro 6,1? The mp 6,1 has 2 GPU's, and I don't understand how work load is split between them. From what I've been able to read the second GPU is not really utilized by most software. I'm considering purchasing a mp 6,1 for an engineering office. I was thinking perhaps if the GPU could be selected to be independent of the second gpu the VM might be somewhat more independent of host OS.