7 Replies Latest reply on Aug 10, 2011 3:03 PM by yongjun

    About frequency change in a tile

    yongjun

      Hi.

       

      I've tried changing tile-frequencies by setting GCU bits in configuration registers, and I think I've succeeded in doing so.

      However, I encountered with a problem.

       

      I tested with a program that just has a simple for-loop if the frequency changes all right.

      I ran the test program like this : "time ./test".

       

      The default frequency of the SCC cores is 533MHz.

      When a core's frequency is 533MHz as default, the "time ./test" result was about 2 seconds, and it actually took about 2 seconds.

      After setting the core's frequency to 100MHz, the "time ./test" result did not change and it was again about 2 seconds.

      But the actual time taken was about 10~11 seconds, this is the time I measured with my watch.

       

      I tested it with another simple test program, which has just "sleep(2);" in the main function, but the result was the same.

      The actual time the program takes changes as expected, so I presume that the frequency changes all right.

      But the result of "time" command would not change.

       

      I'm guessing that somehow the linux or some timimg mechanism seems to think that the frequency is still 533MHz as default.

      Am I right?

       

      Is there a way to tell linux or something that some tile's frequency has changed?

       

      I would like some help! Thank you.