Q. What is the processor compatibility setting in Hyper-V R2?

A. It isn't possible to migrate a virtual machine (VM) between Intel and AMD processors using Quick or Live Migration due to the completely different architecture and instruction sets of the processors. By default, you also can't migrate between different versions of the same processor family because, although both processors may be made by the same company, they could have different capabilities and instructions. The problem arises because some applications perform tests when they start to check the capabilities of the processor. If an application checks the processor and decides it has a certain set of instructions, and then the application's VM is moved to a server that doesn't support a particular instruction using Quick or Live migration, when the application calls an instruction the application may crash.

To resolve this problem, Hyper-V R2 adds the ability to hide many higher-level functions of processors from guest OSs. With this setting enabled, you can move guest OSs between nodes in a cluster even if the nodes have different processor versions because the virtual OSs are only exposed to the generic instructions that are present in all versions of the processor family. Note that the setting doesn't scan the processors and expose the lowest common set of functionality of all the processors in the cluster—it just limits VMs to a generic basic instruction set lower than all the processors in the cluster.

To access the settings for a VM, select Processor for that VM in Hyper-V Manager and enable Migrate to a physical computer with a different processor version, as shown here.

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