Set AFFINITY of a game

I have searched a lot but couldn't find the command to set the affinity of a process that is already running.

All the examples i came across are to start a program with desired affinity but none showed how to change the affinity of a program already running.

For example i have notepad.exe running and i want it to use only core 2 and three. What cmd command can be used for that

In task manager, in the processes tab search the process. The context menu contains a "set affinity" option that allows to chose which CPUs will run that program.

^ Normal way.

But he asked for a command prompt parameters so he wouldn't do that everytime.

Try these:

Set affinity with start /AFFINITY command on Windows 7 - Stack Overflow

or

Start an Application Assigned to a Specific CPU in Windows 7, 8, or Vista

RoasterMen said:

^ Normal way.

But he asked for a command prompt parameters so he wouldn't do that everytime.

Try these:

Set affinity with start /AFFINITY command on Windows 7 - Stack Overflow

or

Start an Application Assigned to a Specific CPU in Windows 7, 8, or Vista

Thanks for the link but again these are to start a program with defined affinity not to set the affinity of a program thats already running

Well, unfortunately there isn't one.

RoasterMen said:

Well, unfortunately there isn't one.

O There is to set a priority but none there to set affinity i should goto microsoft then !

NirCmd can do this. One of its multiple options precisely involves sets the CPU affinity of existing processes:
NirCmd Command Reference - setprocessaffinity

PowerShell can set a process' affinity. See SO answer.