Every so often, Intel and AMD release new processors.Each new generation of processors differs from earlier ones through the inclusion of architectural changes and new processor features.Suppose you have Intel penryn based Vmware host and add another host with Intel Nehalem-based processor.
Unless you take special steps you will be unable to do the Vmotion.In order to enable a mixed-processor VMware cluster to support vMotion to any and all hosts, the hosts must be configured to some kind of least common denominator
This is the job of Enhanced vMotion Compatibility (EVC) which allows you to migrate running virtual machines between different generations of processors.
Once you’ve enabled the EVC feature in an ESX cluster, each host is configured to present only the CPU features of the selected processor type
One thing that EVC does not do is enable you to vMotion virtual machines between AMD and Intel processors. At the very least, you must make sure that all of your ESX hosts are using CPUs from the same manufacturer.
