You can disable the Advance Configuration and Power Interface (ACPI) C-states by using a BIOS firmware option on the computer. If the firmware does not include this option, a software workaround is available. You can disable the ACPI C2-state and C3-state by setting a registry key. To do this, follow these steps:
- At a command prompt, run the following command:
reg add HKLM\System\CurrentControlSet\Control\Processor /v Capabilities /t REG_DWORD /d 0x0007e066
- Restart the computer.
Note The computer idle power consumption will increase significantly if the deeper ACPI C-states (processor idle sleep states) are disabled. Windows Server 2008 R2 uses these deeper C-states on the Xeon 5500 series as a key energy-saving feature.
To continue to benefit from these energy-saving states, remove the registry key that you set in step 1 after you install the hotfix that this article describes. To do remove the registry key, follow these steps:
- At a command prompt, run the following command:
reg delete HKLM\System\CurrentControlSet\Control\Processor /v Capabilities /f
- Restart the computer.