Running Microsoft Windows 2003 32-bit guest operating systems with the /3GB switch in boot.ini results in performance or stability issues
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Running Microsoft Windows 2003 32-bit guest operating systems with the /3GB switch in boot.ini results in performance or stability issues


Article ID: 309208


Updated On:


VMware vSphere ESXi


If you boot a Microsoft Windows 2003 guest operating system with the /3GB switch defined in the boot.ini file on VMware ESX 4.1, you may experience these symptoms:
  • Read or Write memory errors occur in the guest operating system.
  • A Remote Procedure Call (RPC) error is reported and the virtual machine is forced to reboot frequently.
  • A Stop Code type of 0x000000F4 occurs.
  • P2V Conversion fails at 98% with the error:

    unable to create \\.\vstor2-mntapi-shared.xxxx
  • Microsoft .NET or Java applications fail with memory errors.
  • The Microsoft Windows Event log shows errors similar to:

    Event Type: Error
    Event Source: .NET Runtime
    Event Category: None
    Description:.NET Runtime version 2.0.50727.3615 - Fatal Execution Engine Error (7A0979AE) (80131506)


VMware ESXi 4.1.x Embedded
VMware ESX 4.1.x
VMware ESXi 4.1.x Installable


This issue occurs when performing software instruction set virtualization (Binary Translation) in conjunction with the /3GB switch being set in the guest operating system, on VMware ESX 4.1.
This issue is resolved in the patch release for ESXi/ESX 4.1. For more information, see:
To work around this issue when you do not want to apply the patch, you can change the CPU/MMU Virtualization setting to a hardware instruction set translation method.
To change the CPU/MMU Virtualization setting:
Note: Ensure that the virtual machine is powered off before performing this procedure.
  1. Log in to the VMware vSphere Client.
  2. In the virtual machine inventory, right-click the virtual machine and click Edit Settings. The Virtual Machine Properties dialog appears.
  3. Click the Options tab.
  4. Change CPU/MMU Virtualization under Advanced from Automatic to one of these options:
    • Use Intel VT-X/AMD-V for instruction set virtualization and software for MMU virtualization.
    • Use Intel VT-X/AMD-V for instruction set virtualization and Intel EPT/AMD RVI for MMU virtualization.

      Note: For more information, see the Additional Information section of this article.

  5. Click OK to save your changes.
Note: If this process does not resolve the issue, you may work around it by removing the /3GB switch from the boot parameters of your guest operating system.

Additional Information

Enabling Intel EPT/AMD RVI for MMU virtualization may offer improved performance for most workloads. For more information, see Virtual Machine Monitor Execution Modes in VMware vSphere™ 4.0 and Software and Hardware Techniques for x86 Virtualization.


  • Use software for instruction set MMU virtualization is the default option configured for Microsoft Windows 2003 virtual machines. This alleviates conditions where earlier versions of this guest operating system were prone to high amounts of Advanced Programmable Interrupt Controller (APIC) overhead, affecting performance. Microsoft Windows 2003 SP2 and above should be configured to use hardware instruction set virtualization with Intel VT-x/AMD-V.

  • If the system is Intel-based and configured with pre-Nehalem (Core i7) processors or is AMD-based and configured with pre-third-generation Opteron processors, hardware MMU virtualization using Intel EPT/AMD RVI is not set. In this case, use software for MMU virtualization. Intel EPT is only available in Nehalem processors and later.

  • If the system is equipped with an Intel Nehalem-based processor or a third-generation AMD Opteron and newer, you may configure the virtual machine to Use Intel VT-x/AMD-V for instruction set virtualization and Intel EPT/AMD RVI for MMU virtualization for additional performance enhancements. This depends on the types of workloads performed.

  • EVC cluster configurations that mask Intel VT-x/AMD-V or EPT/AMD RVI instruction sets supersede virtualization options specified in an individual virtual machine's configuration. For example, if a pre-Nehalem system (does not support EPT MMU virtualization) was included with an EVC cluster of Nehalem systems, all hosts in the EVC cluster mask the CPU instruction set to ensure VMotion compatibility. Thus the virtual machines or guests, despite specifying and supporting MMU virtualization, will use VT-x without MMU virtualization support enabled.
Changing the virtual machine monitor mode
boot.ini に /3GB スイッチを設定して Microsoft Windows 2003 (32 ビット)ゲスト OS を実行するとパフォーマンスや安定性が低下する