Which two CPU characteristics must be identical for a successful migration with VMotion between ESX Servers? (Choose two.)

A.
CPU clock speed

B.
CPU stepping

C.
CPU cache size

D.
SSE3 support

E.
CPU vendor

Explanation:
vSphere Resource Management Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0, page 47.

VMotion transfers the running architectural state of a virtual machine between underlying ESX/ESXi hosts.

CPU vendor:
VMotion compatibility means that the processors of the destination host must be able to resume execution using the equivalent instructions where the processors of the source host were suspended. Processor clock speeds and cache sizes might vary, but processors must come from the same vendor class (Intel versus AMD) [E above] and same processor family to be compatible for migration with VMotion.

CPU: CPU stepping
Processor families such as Xeon MP and Opteron are defined by the processor vendors. You can distinguish different processor versions within the same family by comparing the processors’ model, stepping level, and extended features.

In some cases, processor vendors have introduced significant architectural changes within the same processor family (such as 64-bit extensions and SSE3) [D above]. VMware identifies these exceptions if it cannot guarantee successful migration with VMotion.