Yes they are different. VT-d is purely a function of the CPU (passed the BIOS enabling option).
First you will want to look at the output of acpidump | egrep "DMAR|IVRS", then you will also want to very that IOMMU groups don't group your GFX with something that won't be passed through using something like: https://gist.github.com/r15ch13/ba2d738985fce8990a4e9f32d07c6ada