Specifications

Prerequisites
If you intend to lower the EVC mode, power off any currently running virtual machines with a higher EVC
mode than the one you intend to enable. See “Determine EVC Modes for Virtual Machines,” on page 122.
The cluster cannot contain a disconnected host. All hosts in the cluster must be connected and registered on
the vCenter Server.
Procedure
1 Display the cluster in the inventory.
2 Right-click the cluster and select Edit Settings.
3 In the left panel, select VMware EVC.
The dialog box displays the current EVC settings.
4 To edit the EVC settings, click Change.
5 From the VMware EVC Mode drop-down menu, select the baseline CPU feature set you want to enable
for the cluster.
If the selected EVC Mode cannot be selected, the Compatibility pane displays the reason or reasons why,
along with the relevant hosts for each reason.
6 Click OK to close the EVC Mode dialog box, and click OK to close the cluster settings dialog box.
Determine EVC Modes for Virtual Machines
The EVC mode of a virtual machine defines the CPU features that the virtual machine can access. The virtual
machine's EVC mode is determined when it is powered on in an EVC-enabled cluster.
When a virtual machine is powered on, it determines the EVC mode of the cluster in which it is running. If the
EVC mode of the cluster is subsequently raised, the virtual machine does not change its EVC mode until it is
powered off and powered on again. This means that the virtual machines does not make use of any additional
CPU features exposed by the new EVC mode of the cluster until the virtual machine has been powered off and
powered on again.
For example, consider a cluster containing hosts with Intel Xeon 45nm Core™ 2 processors that has been set
to the Intel
®
"Merom" Generation (Xeon
®
Core™ 2) EVC mode. A virtual machine powered on in this cluster
runs in the Intel "Merom" Generation (Xeon Core 2) EVC mode. If the cluster EVC mode is raised to Intel
"Penryn" Generation (Xeon 45nm Core 2), the virtual machine remains at the lower Intel "Merom" Generation
(Xeon Core 2) EVC mode. To use any of the features exposed by the higher cluster EVC mode, such as SSE4.1,
you must power off the virtual machine and power it on again.
You can use the Virtual Machines tab for a cluster or a host to determine the EVC modes of the running virtual
machines.
Procedure
1 Select the cluster or host in the inventory.
2 Click the Virtual Machines tab.
3 If the EVC Mode column is not displayed, right-click on the column titles and select EVC Mode.
The EVC modes of all running or suspended virtual machines are displayed in the EVC Mode column.
Powered off virtual machines and virtual machines that are not in EVC clusters show N/A as the EVC
mode.
vCenter Server and Host Management
122 VMware, Inc.