A Hyper-V update is available to increase the number of logical processors and virtual machines on a Windows Server 2008 x64-based computer

After you install the update, you have to install the updated Integration Components. To do this, open the Virtual Machine Connection in Hyper-V Manager, and then select the Insert Integration Services Setup Disk option on the Action menu. Installation of the Integration Services starts automatically.

Notes

• On a Windows Server 2008-based computer, the updated Integration Services are listed in the Programs and Features item in Control Panel as KB957268.
• On a Windows Vista-based computer, the updated Integration Services are listed in the Programs and Features item in Control Panel as KB957269.

Service Pack Information

To resolve this problem, obtain the latest service pack for Windows Server 2008. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

968849 How to obtain the latest service pack for Windows Server 2008

Update information

The following files are available for download from the Microsoft Download Center:

Update for Windows Server 2008, x64-based versions

Download the 956710 package now.

Release Date: September 23, 2008

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to obtain Microsoft support files from online services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.

Prerequisites

To apply this hotfix, you must have Windows Server 2008 installed on the computer.

Restart requirement

You have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other previously released hotfixes.

Registry information

If you want to run more than 150 virtual machines, follow these steps.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 How to back up and restore the registry in Windows

1. Click Start, type
   regedit in the Start Search box, and then click OK.
2. In Registry Editor, locate the following registry subkey:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\SubSystems
   
   By default, the Windows entry in the subkey has a value that resembles the following:
   %SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,20480,768 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=winsrv:ConServerDllInitialization,2 ProfileControl=Off MaxRequestThreads=16
   Note This value appears all on one line.
3. Right-click the Windows entry, and then click Modify. The Edit String dialog box appears.
4. In the Value data box, locate the
   SharedSection entry, change the third value of this entry from 768 to 1536, and then click OK.
   
   The newly changed Windows entry reads as follows:
   %SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,20480,1536 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=winsrv:ConServerDllInitialization,2 ProfileControl=Off MaxRequestThreads=16

Additional requirement

To start a Windows Server 2008 x86-based virtual machine on a computer that uses a 6-core processor, you also have to install hotfix 950182.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

950182 A computer that is running an x86-based version of Windows Server 2008 or an x86-based version of Windows Vista may use fewer processors than expected if the number of cores on a socket is not a power of 2

File information

The English version of this update has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

The .manifest files and the .mum files that are installed in each environment are listed separately in the "Additional file information for Windows Server 2008 and for Windows Vista" section. These files and their associated .cat (security catalog) files are critical to maintaining the state of the updated component. The .cat files are signed with a Microsoft digital signature. The attributes of these security files are not listed.

For all supported x64-based versions of Windows Server 2008