How to Permanently Set CPU Affinity in Windows 11 & 10 for Optimal Performance

Managing CPU resources effectively is crucial for maintaining optimal system performance, especially when certain applications demand significant processing power. By setting CPU affinity, you can assign specific CPU cores to particular programs, ensuring balanced resource distribution and preventing any single application from monopolizing your system's capabilities. This guide explores various methods to permanently set CPU affinity for programs in Windows 11 and 10, providing step-by-step instructions and highlighting the benefits and potential drawbacks of each approach.

Understanding CPU Affinity​

CPU affinity, also known as processor affinity, refers to the assignment of a process or thread to a specific central processing unit (CPU) or a set of CPUs. By default, Windows dynamically distributes processes across all available CPU cores to optimize performance. However, manually setting CPU affinity can be beneficial in scenarios where:

• Performance Optimization: Certain applications may perform better when restricted to specific cores, reducing context switching and cache invalidation.
• Resource Management: Allocating specific cores to resource-intensive applications can prevent them from affecting the performance of other programs.
• Compatibility Issues: Some legacy applications may not function correctly on multi-core systems and require restriction to a single core.

Temporary Method: Using Task Manager​

Before delving into permanent solutions, it's essential to understand how to set CPU affinity temporarily using Task Manager:

• Open Task Manager: Press Ctrl + Shift + Esc to launch Task Manager.
• Navigate to Details Tab: Click on the "Details" tab to view all running processes.
• Set Affinity:
• Right-click on the desired process and select "Set affinity."
• In the "Processor affinity" window, select the CPU cores you want the process to use and click "OK."

Note: This setting is temporary and will reset once the application is closed or the system is restarted.

Permanent Methods to Set CPU Affinity​

To make CPU affinity settings persistent across sessions, consider the following methods:

Method 1: Creating a Shortcut with Affinity Parameters​

By creating a customized shortcut, you can launch an application with specific CPU affinity settings:

• Create a New Shortcut:
• Right-click on the desktop and select "New" > "Shortcut."
• In the location field, enter the following command:
  cmd.exe /c start "ProgramName" /affinity [HexValue] "C:\Path\To\Program.exe"
  Replace "ProgramName" with a desired name, [HexValue] with the hexadecimal value representing the desired CPU cores, and "C:\Path\To\Program.exe" with the full path to the application's executable file.
• Determine the Hexadecimal Affinity Mask:
• Each CPU core corresponds to a bit in a binary number. For example, to assign cores 0 and 1, the binary representation is 11, which equals 3 in hexadecimal.
• Use the following table to determine the appropriate hexadecimal value:
  

  Cores Used	Binary Mask	Hexadecimal Value
  Core 0	0000 0001	1
  Core 1	0000 0010	2
  Cores 0-1	0000 0011	3
  Cores 0-2	0000 0111	7
  Cores 0-3	0000 1111	F

• Complete the Shortcut Creation:
• Click "Next," name the shortcut, and click "Finish."
• Optionally, right-click the shortcut, select "Properties," and click "Change Icon" to customize the shortcut's appearance.

Note: This method is effective for applications that you launch manually via the shortcut. However, it may not work for processes initiated by other programs or system services.

Method 2: Using Process Lasso​

Process Lasso is a third-party utility designed to manage CPU affinity and priority settings persistently:

• Download and Install Process Lasso:
• Visit the official Process Lasso website and download the installer.
• Follow the installation instructions to set up the application.
• Configure CPU Affinity:
• Launch Process Lasso and locate the target application in the process list.
• Right-click on the process, navigate to "CPU Affinity," and select "Always."
• Choose the desired CPU cores for the application.

Note: Process Lasso will automatically apply the specified CPU affinity settings each time the application is launched, ensuring persistence across sessions.

Method 3: Modifying the Windows Registry​

For advanced users, modifying the Windows Registry can set CPU affinity permanently:

• Open Registry Editor:
• Press Win + R, type regedit, and press Enter.
• Navigate to the Target Key:
• Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options.
• Create a New Key:
• Right-click on "Image File Execution Options," select "New" > "Key," and name it after the application's executable file (e.g., notepad.exe).
• Set the Affinity Mask:
• Within the new key, right-click, select "New" > "DWORD (32-bit) Value," and name it AffinityMask.
• Double-click AffinityMask, select "Decimal," and enter the decimal equivalent of the desired affinity mask.

Caution: Modifying the registry can affect system stability. Ensure you back up the registry before making changes.

Method 4: Utilizing PowerShell Scripts​

PowerShell scripts can automate the process of setting CPU affinity:

• Create a PowerShell Script:
• Open Notepad and enter the following script:
  

  $process = Start-Process -FilePath "C:\Path\To\Program.exe" -PassThru
  Start-Sleep -Seconds 1
  $process.ProcessorAffinity = [Convert]::ToInt32("11", 2)

  Replace "C:\Path\To\Program.exe" with the application's path and "11" with the binary representation of the desired cores.
• Save and Execute the Script:
• Save the file with a .ps1 extension (e.g., SetAffinity.ps1).
• Run the script using PowerShell with administrative privileges.

Note: This method requires running the script each time you want to set the affinity, unless automated through Task Scheduler.

Considerations and Best Practices​

• System Stability: Restricting applications to specific CPU cores can lead to performance issues if not configured correctly. Monitor system performance after applying affinity settings.
• Application Behavior: Some applications are designed to utilize multiple cores efficiently. Limiting their core usage may degrade performance.
• Testing: Before applying permanent changes, test affinity settings temporarily using Task Manager to observe their impact.

By implementing these methods, you can effectively manage CPU resources, ensuring that critical applications receive the necessary processing power while maintaining overall system performance.

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Source: H2S Media How to Permanently Set CPU Affinity for a Program in Windows 11 or 10