While trying to set up IOMMU, I came across a post that mentioned that you need not just software but also hardware support for it to work. The hardware support includes not just the CPU but also the motherboard/chipset.
Since you need VT-d for IOMMU, I checked the compatibility of my CPU (4790K) and motherboard and found something interesting which I can't explain.
My motherboard "GA-Z97X-UD3H" has the Z97 chipset which according to Intel's ark doesn't support VT-d, however the board offers me VT-d in the BIOS and its close brother, the "GA-Z97[X]-UD5H" is even listed as an IOMMU-supported motherboard on Wikipedia.
Now my question is, how is it possible that the chipset officially doesn't support VT-d but the motherboard still offers it? Can motherboard manufacturers add this kind of functionality themselves? Or what is going on?