On more than one occasion, I have built a new ESX host system and had immediate migration issues with 64-bit guest operating systems. This is due to an easy-to-forget BIOS default that disables 64-bit processing. To save you the hassle of trying to diagnose why the migration may fail, here is a specific configuration that can prevent this issue.
The symptom is that the virtual machine migration of a 64-bit guest VM fails with the “CPU on host is incompatible with CPU feature requirements of virtual machine” message due to the lack of 64-bit support on the BIOS. To resolve the configuration issue, check the server’s processor configuration to ensure that proper support is enabled. On Dell PowerEdge series servers, the option to enable the functionality so that ESX permits the 64-bit migrations correctly is shown below:
This option can be accessed by pressing F2 during the boot process to gain entry into the BIOS. Go to the CPU Information section to enable the 64-bit support functionality option. Check your server documentation for other platforms.
Once this setting is enabled, you can migrate the 64-bit virtual machines without issue. This situation makes advanced testing on BIOS updates on your ESX servers a very good idea as the migration functionality may be impacted. More information on this issue and related processor topics related to this are discussed on a VMware Communities thread.