VxRail: What is the Enhanced vMotion Compatibility EVC mode

What is the EVC?
EVC is short for Enhanced vMotion Compatibility. EVC allows client to migrate virtual machines between different generations of CPUs.

What is the benefit of EVC?
EVC allows user to migrate virtual machines between different generations of CPUs. With EVC users can mix older and newer server generations in the same cluster and be able to migrate virtual machines with vMotion between these hosts. This makes adding new hardware into your existing infrastructure easier and helps extend the value of your existing hosts. With EVC, full cluster upgrades can be achieved with no virtual machine downtime whatsoever. When adding new hosts to the cluster, migrate the virtual machines to the new hosts and retire the older hosts.

How do I use EVC?
EVC is enabled for a cluster in the VirtualCenter or vCenter Server inventory. After it is enabled, EVC ensures that migration with vMotion is possible between any hosts in the cluster. Only hosts that preserve this property can be added to the cluster.

How does it work?
After EVC is enabled, all hosts in the cluster are configured to present the CPU features of a user-selected processor type to all virtual machines running in the cluster. This ensures CPU compatibility for vMotion even though the underlying hardware might be different from host to host. Identical CPU features are exposed to virtual machines regardless of which host they are running on, so that the virtual machines can migrate between any hosts in the cluster.

Can migrations with vMotion still fail for virtual machines within an EVC cluster?
Yes: More factors than CPU compatibility are used to determine vMotion compatibility. For example, if the virtual machine does not reside on storage shared by the source and destination hosts. Then migration with vMotion cannot occur between these hosts.

Enhanced vMotion Compatibility (EVC) simplifies vMotion compatibility issues across CPU generations. EVC automatically configures server CPUs with Intel FlexMigration or AMD-V Extended Migration technologies to be compatible with older servers.

After EVC is enabled for a cluster in the vCenter Server inventory, all hosts in that cluster are configured to present identical CPU features and ensure CPU compatibility for vMotion. The features presented by each host are determined by selecting a predefined EVC baseline. vCenter Server does not permit the addition of hosts that cannot be automatically configured to be compatible with the EVC baseline.

EVC does not allow for migration with vMotion between Intel and AMD processors.

EVC and CPU Compatibility FAQ VMware article VMware EVC and CPU Compatibility FAQ
All the VMs must be taken down to make the change. There are instructions to change it from VMware.

EVC is enabled on VxRail by default.
Dell VxRail Tech Book 
EVC mode can be changed if the customer desires. See the SolVe procedure for how to "Change the VxRail Cluster EVC Mode."