I find this post very interesting.

I've made some tests with ESXi (5.0 and 5.1) with AMD and Intel desktop boards. I work at IBM and I have worked with different environments using IOMMU, but on desktop boards, as you already stated, it kinda hit or miss.

I have and FM1, and can confirm that it does not support AMD-Vi, but I read in official documents that FM2 and A85X supports it. I wanted to migrate my FM1 hardware to FM2, but I don't have the money right now. So, I do not know of any board actually supporting AMD-Vi, but I know the platform has support for it. We could ask several of the users in this forums who have FM2 boards to search the option to enable or disable the IOMMI virtualization within BIOS, and make a list. That would be very helpful, 'cause as you said, a lot of people search for this info on forums or the internet and nobody can give a straight answer.

On AM3, I did have some kind of success playing with AMD-Vi. One of my other systems is a Phenom II X6 1055T on an Asrock 890FX Deluxe 4. I didn't have much time, because I had to make only non-destructive tests on that machine, and only tried once. There is (was?) a bug with Pass-through on ESXi 5.1 at that time, the USB controller failed to pass to the VM, but a NIC was working. Didn't have time to test anything else.

As you know, the only way to use VT-d with Intel is giving up on overclocking, because K series on LGA1155 does not support it, or going for LGA2011. I have two Intel rigs, a 1156 with a Core i3 530 and my primary system with an i7 3820. With LGA2011 you need C2 stepping to have VT-d, if you go for a 3930K or 3960X.

With the 3820 I've made a lot of tests, with my HD7950, USB controllers, and even with the Creative X-Fi XtremeGamer, which barely works in a non-virtual environment. I have a Gigabyte X79-UD3, which supports VT-d, and everything works perfectly, except for the X-Fi.

The i3 530, as you know, does not support VT-d, but the Core i5 series does. I can't get my hands on a LGA1156 i5, that isn't expensive as a brand new i5, so I couldn't test?it, but the motherboard that I have, BIOSTAR TH55B HD, supports VT-d in the BIOS.