Cannot Select MPS Uniprocessor or ACPI Uniprocessor HAL (811366)


The information in this article applies to:

  • Microsoft Windows Server 2003, Standard Edition
  • Microsoft Windows Server 2003, 64-Bit Datacenter Edition
  • Microsoft Windows Server 2003, 64-Bit Enterprise Edition
  • Microsoft Windows Server 2003, Datacenter Edition
  • Microsoft Windows Server 2003, Enterprise Edition
  • Microsoft Windows Server 2003, Web Edition
  • Microsoft Windows XP Professional
  • Microsoft Windows XP Home Edition
  • Microsoft Windows Small Business Server 2003, Premium Edition
  • Microsoft Windows Small Business Server 2003, Standard Edition

SYMPTOMS

If you remove a processor from a multiprocessor computer or turn off hyperthreading support in the BIOS, and then try to change your Hardware Abstraction Layer (HAL), you only have the following options:

If the MPS Multiprocessor HAL is currently installed you can change to the following options:
  • Standard PC
  • MPS Multiprocessor

If the ACPI Multiprocessor HAL is currently installed you can change to the following options:
  • Advanced Configuration and Power Interface (ACPI) PC
  • ACPI Multiprocessor
  • MPS Multiprocessor
You do not have the option to switch to MPS Uniprocessor or ACPI Uniprocessor.

CAUSE

This behavior occurs because Windows Server 2003 and Windows XP only permit you to change to reliable HAL types.

WORKAROUND

To switch to a uniprocessor HAL, reinstall the operating system.

MORE INFORMATION

In Windows 2000, you can change to any listed HAL type. However, if you select an incorrect HAL, the computer may not start correctly. Therefore, only compatible HALs are listed in Windows Server 2003 and Windows XP. If you run a multiprocessor HAL with only a single processor installed, the computer typically works as expected, and there is little or no affect on performance.
Modification Type:MajorLast Reviewed:12/19/2003
Keywords:kbprb KB811366
©2003 Microsoft Corporation. All rights reserved.