This isn’t actually specific to either a Dell PowerEdge R720 or an E5-2690 CPU, any system with an E5-2600 series CPU will likely be in scope of this post.
The trick to getting your VMs to change their EVC mode to Sandy Bridge from somethine a little older such as Westmere is twofold:
- The host must be running ESXi 5.0 or higher, ESX(i) 4.1 update 2 and older don’t support Sandy Bridge.
- The VM hardware version must be upgraded to 8.
The latter requires the VM to be powered off, and in the case of Windows Server 2008 and higgher, a further reboot a few minutes after power on once Windows has detected the new CPU.