Smart hardware choices?

Dear TekSyndicate,

With the new RedHat technology for nVidia graphics and AMD Mantle on the one hand, and SteamOS, ever more games using open source technology, ever more mainstream productivity software using open source graphics card functionality (Adobe OpenGL, LibreOffice Calc using OpenCL, Darktable/Blender/GIMP using OpenGL/OpenCL), etc... on the other hand, it would be great to have an overview of hardware that supports these new technologies.

I know there is a lot of (voluntary) confusion about all of this, but there is one technology that seems vital for all of the above, and that's IOMMU.

I'm a linux user, so I've been searching for IOMMU compatible hardware since the day it came out, because I want to use hardware virtualization, but especially with Intel socket 1155/1150 hardware, it's a real struggle to even obtain information on whether or not IOMMU will work on CPUs or motherboards. Basically, all that's available, is user experience shared on different linux fora, which amounts to the general conclusion that "k" CPUs and proprietary PLX PCIe controllers (as used by Asus) block IOMMU, but there seem to be exceptions, and nothing is really documented either by Intel, or by motherboard manufacturers. There is no actual 100% valid confirmation, Intel might say that a chipset or CPU has VT-d, but that doesn't mean that IOMMU actually works, because the BIOS (mostly UEFI) or PCIe controllers may not support it, and VT-d isn't enough for IOMMU to work because "VT-d" is just an extension, not an IOMMU compatibility indication like AMD-Vi for instance. So I've been using AMD systems and socket 2011 systems with legacy BIOS because they have IOMMU, but sometimes, there is no way past Haswell, for instance for laptops or for low power mITX systems, and I would want to build a Haswell-based system with the IO capabilities offered by the Z87-chipset, but only if IOMMU actually works, and there is not much reliable info on this for that hardware. Haswell CPUs have some interesting new virtualization features that offer a real benefit over AMD, but they are of no use when IOMMU is not supported.

So the question is: in the light of IOMMU as the main backbone technology for graphics card optimization (and of course kvm, which is very useful for being able to safely continue playing legacy games on Windows without performance loss), what Haswell-based hardware is recommended in order to make sure (the next series of) nVidia cards will be able to work efficienly (this will require IOMMU) and will AMD Mantle also require the graphics card to be able to access the system RAM directly for maximum performance (which is a given with AMD systems, but still a question with Intel CPU+AMD GPU systems), and therefore need IOMMU?

Thanks in advance for creating some clarity on this subject. I'm sure it's a very important issue for most users, even though few are aware of it even being an issue.

Kind regards,