XenServer 7.0 introduced improved support for Heterogeneous Pools which enables live migration across different CPU types of the same vendor (requires AMD Extended Migration or Intel Flex Migration), details here: http://bit.ly/1ADu7Py.
This capability is maintained in XenServer 7.3
Product :
Citrix, XenServer/7.3, Enterprise
Feature :
Migration Compatibility, VM Mobility, VM Mobility and HA