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VMotion CPU Compatibility Requirements for AMD Processors (1992)

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This articles outlines migrating virtual machines with VMotion across AMD processors, and the necessary steps to take to ensure compatibility.


In ESX 3.5 Update 2 and later, VMware recommends using EVC to eliminate many VMotion CPU compatibility problems. For more information on EVC, see KB 1003212.

To ensure production-system stability during migration with VMotion, VirtualCenter and vCenter Server require the source and target CPUs to be compatible. For more information on CPU compatibility requirements, see Basic System Administration for your version of VirtualCenter or vCenter Server, available from

If the source and target CPUs are incompatible for VMotion, you can:

  • Perform a cold migration (rather than a VMotion migration), thereby removing VMotion CPU requirements as an issue.
  • Remove VMotion compatibility constraints by modifying the default bit-mask used by VirtualCenter or vCenter Server. Note that some modifications discussed in this article are neither supported nor recommended by VMware for production environments. In general, masking any CPU features intended for applications (such as SSE3) is not supported for VMotion. Use of EVC is recommended for migrating virtual machines across CPU generations.

To obtain more information about a host system's CPU, you can use the CPU Identification Utility. VMware provides this utility as an ISO image file that can be uncompressed and used to create a bootable CD-ROM that provides CPU information about a host, even before an operating system or ESX is installed. The latest version of this tool can be found on the VMware downloads page at

This article discusses VMotion compatibility constraints for AMD CPUs. For detailed information about how to apply the masks discussed in this article, see knowledge base article 1993, “Migrations with VMotion Prevented Due to CPU Mismatch—How to Override Masks.” For information on Intel CPUs, see KB 1991.

VMotion Compatibility Groups for AMD Processors

To guarantee successful migration with VMotion, VMware has defined several compatibility groups based on the AMD Opteron processor family. By default, VirtualCenter and vCenter Server support VMotion migrations within each CPU compatibility group. For example, migration within group A is allowed, but migration from group A to group B or from group B to group C is not, as shown in the table.

AMD Opteron/Athlon 64 CPU Family

VMotion CPU

CPU Details

ESX Server 3.x and ESX 4.x

ESX Server 2.x

Group A

(Groups A and B are the same for VC 1.x)

Revision C, without SSE3.

Models include:

130nm versions.
For example, Sledgehammer.

For A <-> B VMotion, apply FFXSR mask. (Not supported.)

For A <->D VMotion, apply SSE3 mask. (Not supported.)

Group B

(Groups A and B are the same for VC 1.x)

Revision D, without SSE3.

Models include:
90nm versions.

For B <-> C VMotion, apply SSE3 mask. (Not supported prior to ESX 3.5. Experimentally supported for ESX 3.5 and later only.)

Group C
(Groups C and D are the same for VC 1.x)

Revision E, with SSE3.

Models include: AMD Opteron Generation 1. For example, AMD Opteron 1xx, 2xx, 8xx.

For C <-> D VMotion, apply RDTSCP mask for 32-bit guests. (Not supported prior to ESX 3.5. Experimentally supported for ESX 3.5 and later only.)

For 64-bit guests, apply RDTSCP and CMPXCH16B masks. (Not supported prior to ESX 3.5. Experimentally supported for ESX 3.5 and later only.)

Group D

(Groups C and D are the same for VC 1.x)

Revision F, with SSE3 and RDTSCP.

Models include: AMD Opteron Generation 2. For example, AMD Opteron 12xx, 22xx, 82xx.

AMD K10 Opteron and later CPUs

VMotion Compatibility GroupCPU DetailsESX/ Server 3, ESX/ESXi 4.x, and ESXi 5.xESX Server 2.x
Group A

All supported AMD K10 CPUs.

Models include: AMD Opteron Generation 3. For example, AMD Opteron 13xx, 23xx, 24xx, 83xx, 84xx
For A <--:> B and A <--> C migration, apply 3DNOW mask.

Group B
AMD Opteron™ Generation 4These processors are supported for ESXi 5.x only.
Group C
AMD Opteron™ "Piledriver" GenerationThese processors are supported for ESXi 5.x only.

Applying the Masks

For information about how to apply masks referenced in the table, see KB 1993 under the section titled "Modifying the Default Mask."

Warning: For production environments, VMware neither supports nor recommends modifying CPU masks for SSE3, SSSE3, RDTSCP, or CMPXCHG16B, because of the risk of failure in applications or the guest operating system after migration. Experimental support is available for some masks in ESX 3.5 and later as noted. For more information on experimental feature support, see

VMotion Between Single-Core and Multi-Core Processors

Migrations between single-core and multi-core AMD processors are supported, as long as the source and target CPUs have compatible CPU features (or the features are masked) as outlined in the tables above.

For More Information

For more information about the AMD Opteron processor family, see,,30_118_8796,00.html.

Note: Knowledge base articles 1991, 1992, and 1993 replace article 1377.

Additional Information

For translated versions of this article, see: 


cannot-vmotion different-amd-cpu incompatible-cpu migrate-vm-across-esx-hosts multi-core single-core unable-to-migrate-vm vmotion-vm


URLZ; 1992; dual core; dualcore

Update History

06/21/2012 - Updated for 5.x

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