Was reading some docs over past few days. Seems that VT-d or any virtualization features from BIOS has performance impact when it is enabled, even if not being used. Most of the data comes from gaming, disabling increased FPS around 3-8% (using video from cpu, etc).
So if you like to do performance testing, do tests with VT-d enabled and the disabled. Most times BIOS will have it enabled by default.
Obviously this does not apply for those who must have it enabled for VM's, but not every Hyper needs to have VT-d for VM's to work, so that's something also to look into.