Does Xeon westmere ep (xeon 56xx series) have vt-d (=iommy / direct io) or does intel TXT (Intel® Trusted Execution Technology) include vt-d?

I'm at a loss. I've been researching current processors for an important project for some time now.

I need to know, if the xeon 5600s (Westmere EP) include vt-d (iommu/directed io/pci passing) because the system will run virtualized guests. This enables direct hardware access eg. pci passthrough, in xen for example.

It seems that the 5600s TXT should incorporate vt-d and that xeon 5600s should include vt-d as they are ramped up 5500s, but there is no conclusive answer anywhere. Intel's processor comparison only states that 5500s have vt-d and no TXT and 5600s have no vt-d but TXT.

I'd be really grateful if anybody could clear this up and possibly even provide a citation.

Thanks a lot.