If you are running any one of the following operating systems on a computer that has multiple processors, the processor load is not distributed across the multiple processors:
Microsoft Windows Server 2003, Web Edition
Microsoft Windows Server 2003, Standard Edition
Microsoft Windows Server 2003, Enterprise Edition
Microsoft Windows Server 2003, 64-Bit Enterprise Edition
Microsoft Windows 2000 Advanced Server
Microsoft Windows 2000 Server
Microsoft Windows NT Server 4.0
Specifically, the resources of one processor are used much more than the other processor or processors that are in your computer. Additionally, if you use a Microsoft Windows-based client computer to connect to the server that is running one of these operating systems, you receive one of the following error messages:
System error 64 has occurred. The specified network name is no longer available.
System error 121. The semaphore timeout period has expired.
System Error 240 hasoccurred, the session was canceled.
This issue occurs because your network is very busy. For example, your network may be very busy if many client computers are copying files to the server. By default, the registry setting for the processor affinity mask does not specify that the operating system must search for any available processors that can be used when many network-related requests occur. This is true for the operating systems that are listed in the "Symptoms" section.
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
To resolve this issue, change the value of the ProcessorAffinityMask entry in the registry to match the number of processors that are in your computer. To do this, follow these steps:
Click Start, click Run, type regedit, and then click OK.
Right-click ProcessorAffinityMask, and then click Modify.
In the Value data box, type one of the following values, and then click OK:
If you have two processors, use the binary value 0b11, or hex value 0x3.
If you have three processors, use the binary value 0b111, or hex value 0x7.
If you have four processors, use the binary value 0b1111, or hex value 0xF.
Quit Registry Editor.
Note The 0x0 or 0xFFFFFFFF values are used to disable the ProcessorAffinityMask entry.
The ProcessorAffinityMask entry in the registry specifies the processors that can be associated with a network adaptor. Additionally, this entry can process the delayed procedure calls (DPCs) that are generated by that network adaptor.
The ProcessorAffinityMask entry is designed for computers that have multiple processors and that have multiple network adaptors.
Each bit of the 32 bits in the value of this entry represents one processor. The high bit represents processor 32, and the low bit represents processor 0.If a bit is set to 1, the processor that is represented by the bit can be associated with a network adaptor. The processor that is represented by the bit can also process all the DPCs that the associated network adaptor generates.
If a bit is set to 0, the processor that is represented by the bit cannot be associated with a specific network adaptor.
If a network adaptor is not associated with a processor, the network adaptor's DPCs are processed by the same processor that processed the interrupt where the DPC evolved.
Caution If you modify the ProcessorAffinityMask, you should check for possible side effects on Receive-side scaling (RSS) settings. Receive-side scaling (RSS) allows for the network load from a network adapter to be balanced across multiple CPUs. In this case, RSS may have to be configured on systems where network processing is restricted to a subset of the processors in the system.
More information about RSS is available in the "Scalable Networking with RSS" white paper. To review this white paper, visit the following Microsoft Web site:
Microsoft Windows Server 2003, Web Edition, Microsoft Windows Server 2003, Standard Edition (32-bit x86), Microsoft Windows Server 2003, Enterprise Edition (32-bit x86), Microsoft Windows Server 2003, Enterprise x64 Edition, Microsoft Windows 2000 Server, Microsoft Windows 2000 Advanced Server, Microsoft Windows NT Server 4.0 Standard Edition