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windows 7 does not allow creation of more than 2 groups in an 8 core system RRS feed

  • Question

  • I have a intel r xeon r cpu w3565 system. I am running a 64 bit windows 7 on top of it.

    with no group awareness the task manager shows 8 logical cores as needed(4 cores and 8 threads).

    Now if I need 4 groups with 2 prcessors each I did this:

    bcdedit/set groupsize 2 and restarted my machine. I could see 2 groups with 2 logical processors each. I also ran a small test program :

    #include <windows.h>
    #include <stdio.h>

    int main(int argc, char *argv[]) {  
        WORD numProcs
    = 0,i;    
       
    int sum=0;
        numProcs
    = GetActiveProcessorGroupCount();  

       
    for(i=0;i<numProcs;i++)
       
    {
             
    int procs;
             procs
    =GetActiveProcessorCount(i);        
             printf
    ("\ngroup %d count :%d\n",i,procs);      
             sum
    += procs;  
       
    }  
        printf
    ("numProcs: %d\n", sum);    char abc;    scanf("\n%c",&abc);  
       
    return 0;
    }

    Which also gave core count as 4. earlier this gave it as 8(without group awareness on)

    Now if I set group size to 4 I get 2 groups with 4 cores each. and my test program output is 8 this time.

    I then set groupsize to 1 and this time I again got 2 groups with a single logical core in each core.

    I am unable to understand why windows cannot expand the number of groups to 4 when actually the documentation says that it can go max uptil 4.

    Any idea what I am missing here?

    Monday, August 13, 2012 10:42 PM