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µVISION: Dual Processor PCs and µVISION

Information in this knowledgebase article applies to:

  • C51 Version 8.00 and later
  • C251 Version 4.01 and later
  • C166 Version 6.00 and later
  • MDK-ARM Version 3.00 and later


When running µVision on a PC equipped with multiple processors, the CID displayed in File — License Management changes when µVision is closed, then immediately opened again. Attempts to build a project results in the following license error:



On PCs with multiple processors, WindowsXP, Windows Vista and Windows 7 (32- and 64-bit) try to automatically assign an application to any available processor. µVision is designed to license and run on the same processor. When the licensed processor differs from the running processor, license verification flags this as an illegal condition, and displays the R201 error.

Important Note:

  • This only applies to PCs with multiple processors, not multiple cores. Single processor, multi-core PCs are considered legal during license verification.


Windows Vista and Windows 7

For Windows Vista and Windows 7, create a shortcut with the following in the command line:

C:\Windows\System32\cmd.exe /C START "Uv4" /AFFINITY 1 "C:\Keil\UV4\Uv4.exe"

The /AFFINITY value of 1 in the START command forces µVision to run in the first core of the first processor. The /AFFINITY value is a hex number with each bit corresponding to a core. For a PC with 2 quad-core processors, an /AFFINITY value of F, selects the all 4 cores in the first processor.  Likewise, an /AFFINITY value of F0, selects all 4 cores in the second processor.

For the best results with µVision, select all the cores of 1 processor, and no cores in the other processor.  For example, for a PC with 2 dual-core processors, use an /AFFINITY value of 3 to use both cores of the first processor,  or C to use both cores of the second processor.  But remember, a value of F for this example, will result in the R201 error.

Windows XP

Windows XP's version of the START command, does not support the /AFFINITY option. For Windows XP, download the psexec.exe utility from Microsoft SysInternals, and install it in your PC's path. Then, create a shortcut with the following in the command line:

psexec.exe -a 1 cmd /c "C:\Keil\UV4\Uv4.exe"

The number after the "-a" designates the processor that will run µVision.


Last Reviewed: Wednesday, June 21, 2017

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