What type of Legacy PCI cards are you referring too? Are using Linux or Windows OS?
This Wiki page list all the CPU and Motherboards that support IOMMU for AMD vi or Intel VT-d : List of IOMMU-supporting hardware - Wikipedia .
Thanks for the replay! It's a custom-made, proprietary HW (basically a signal tester device), not a massmarket one. Its drivers work only on Win98 and Win2K.
I know that list but I just cannot believe that only this few, out of the combinations of the hundreds of CPU and motherboard models, are working. I already checked that list and I have access to many mobos but these are, unfortunately, not among them. Sure, I can find them second-hand if they are really the only ones but I still hope someone had success with other model that I might have...