As your ESXi clusters scale-out, though it is imperative to have CPUs of the same make and model, you could end up having newer servers in the cluster with uncommon processor feature sets. To be able to migrate VMs between hosts in the cluster, it is necessary to guarantee that the CPU feature sets of all the ESXi hosts in the cluster are identical. This is achieved by enabling EVC on an ESXi cluster.

The following diagram will help you with decision-making when you're planning to use EVC: