@ember1205 it's not a matter of not being "well optimized" or xen arbitrarily removing support for old CPUs (we don't do that), it's a matter of the CPUs he's using being so old they're missing entire instruction sets that are required for proper virtualization. The Z800 systems you mention use xeons a full generation newer than the processors he's using, and were the first intel xeon generation to have proper full IOMMU/VT-d/etc instruction set support, so of course I'm sure they worked just great. The Z800 line is the same xeon generation as the 11th gen dells I mentioned, which is why I stated that is the oldest I would comfortably use - any generations older than these (like the poweredges zxcp is using) are missing core instruction sets xen relies upon.
