Windows XP may display incorrect CPU name and CPU speed information in applications that use WMI to recognize processor information

In the System Properties tool in Computer Management or in other applications that use Windows Management Instrumentation (WMI) to recognize processor information, Windows XP may display incorrect CPU name and CPU speed information.

For example, you examine the System Properties tool in Computer Management for Intel Core 2 Duo CPU - E8400 3.0GHz or for Intel Celeron 420. When you do this, the CPU information that Windows XP displays may differ from the actual hardware information.

This issue occurs because Microsoft code currently cannot handle the following fields that are returned from the CPUID instruction:

• The CPUID Extended Model field from the sixteenth bit to the nineteenth bit
• The CPUID Extended Family field from the twentieth bit to the twenty-seventh bit

We use only the fourth bit to the seventh bit for the processor model number.

This issue is caused by changes in the Intel extended model field in the CPUID instruction output. Therefore, we cannot fix all the variants of this issue.

The misidentification of processors is caused by a change in the return value structure of the Intel assembler mnemonic CPUID. When new processors become available and when they are identified by using only the fourth bit to the seventh bit of the structure, the CPU information in the System Properties tool will be correct.

Note Every new processor that uses the Intel extended CPUID output structure will be identified incorrectly.

To work around this issue, do not use WMI to recognize the processor information. Instead, use the FriendlyName registry entry to retrieve the processor information.

To locate the FriendlyName registry entry, 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:

1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\ACPI\GenuineIntel_-_x86_Family_15_Model_<number>\_0
   Note In this subkey, "0" refers to the first CPU in the computer. In a multiprocessor system, "1" refers to the second physical CPU. In a multiple logical core processor system, "1" refers to the second logical CPU.

The information in the FriendlyName registry entry is retrieved from the CPU by using the CPUID instruction from the processor driver. The information is retrieved when the driver is initialized or when the computer is restarted.

If this information changes because of corruption or because of user modifications, this information is updated with information that is returned from the processor or processors. The CPU speed is displayed as the "Brand String" or as the "Friendly Name."

For more information, see the section about CPUID instruction on pages 236 to 238 of the Intel Software Developers Manual. To do this, visit the following Web site:The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.