In simplest terms, “compatible CPUs? for VMotion purposes means that source and target CPUs must have the same manufacturer (Intel or AMD) and be members of the same basic processor family (Pentium 4 or Core, for instance). Within a given processor family, the source and target CPUs must also have certain common and extended features implemented (or not implemented, depending on the specific feature) for VMotion to succeed.
To determine if the source and target CPUs meet VMotion requirements, VirtualCenter compares the target CPU to a default bit mask definition. The default bit mask has evolved with each version of VirtualCenter to support (or preclude) VMotion migration given a specific set of CPU features. For example, the VirtualCenter 1.x bit mask doesn’t flag the NX (Intel) or XD (AMD) bits, but the VirtualCenter 2.x bit mask does.
How do I override VMotion compatibility restrictions for CPU mismatch? By default, VirtualCenter allows migrations with VMotion between compatible source and destination CPUs only. This Knowledge Base article provides information about how to override CPU-compatibility constraints; when it is appropriate to do so; and provides links to additional information and resources.
