CPU resources are not allocated correctly for a virtual machine in Windows 8 or Windows Server 2012

Applies to: Windows 8Windows 8 EnterpriseWindows 8 Pro


When the Hyper-V role is installed on a Windows Server 2012-based computer, or the Hyper-V feature is enabled on a Windows 8-based computer, you experience the following issues. 

Issue 1

When you set the CPU limit on a virtual machine to a value that is 15 percent or less of the total CPU resources on the computer, the virtual machine crashes.

Note This issue does not occur when the virtual machine is running Windows 8, Windows Server 2012, or a later version of Windows.

Issue 2

When you configure the CPU limit on a virtual machine, the virtual machine is allocated less resources than the limit that you configured. For example, if you set the CPU limit on a virtual machine to 20 percent of CPU resources on the computer, the virtual machine is allocated less than 20 percent of CPU resources.


Cause of Issue 1

This issue occurs because the timer clock interrupts are not sent to the virtual machine in time. Therefore, the virtual machine assumes that a hardware error occurred.

Cause of Issue 2

This issue occurs because the hypervisor throttles the resources that are provided to the virtual machine.


This hotfix is also available at Microsoft Update Catalog.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website: Note The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must be running Windows 8 or Windows Server 2012.

Registry information

To use the hotfix in this package, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates