Dynamic Clocks For Radeon R500+

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  • phoronix
    Administrator
    • Jan 2007
    • 67398

    Dynamic Clocks For Radeon R500+

    Phoronix: Dynamic Clocks For Radeon R500+

    When it comes to ATI open-source power management, so far AMD's open-source kindness has just yielded a list of registers but no proper documentation or how PowerPlay exactly works. However, AMD's Alex Deucher has just committed "Dynamic Clocks" support for the Radeon R500 and R600 graphics cards...

    Phoronix, Linux Hardware Reviews, Linux hardware benchmarks, Linux server benchmarks, Linux benchmarking, Desktop Linux, Linux performance, Open Source graphics, Linux How To, Ubuntu benchmarks, Ubuntu hardware, Phoronix Test Suite
  • puntarenas
    Phoronix Member
    • Jun 2007
    • 64

    #2
    This is very interesting but also confusing.

    Originally posted by bridgman
    Originally posted by "puntarenas
    However other reviews tell things still work driver dependent, so if changing power states is still a driver job, does it work with fglrx and will those specifications also become availiable for the RadeonHD team or are these processes completely transparent to the software now?
    My understanding is that there is still some driver involvement, but the new HW capabilities on 6xx parts allow faster and more fine-grained power-down than the driver can do on its own so overall power savings can be improved. We will be making this information available to open source developers. In parallel, support is being added (or has been added) to fglrx although I'm not sure of the exact status.
    Source

    So what I still like to know is which PowerPlay functions are implemented in hardware (and therefore should work on Linux out of the box?!), which functions are driver dependent and which will work with RadeonHD now or soon.

    If you want to leak some more information, I would also like to know when RV770 will arrive

    Comment

    • bridgman
      AMD Linux
      • Oct 2007
      • 13188

      #3
      I don't think anything is completely implemented in hardware. Everything needs to be set up by the driver and AFAIK pretty much everything needs to be enabled and disabled at certain times. The difference with the newer chips seems to be that once everything is set up the hardware can make some of the clock switching decisions without driver intervention, so that power consumption can be adjusted more quickly as the workload changes and more power can be saved as a result.

      Alex is experimenting with the AtomBIOS calls for dynamic clock gating but so far we aren't seeing a lot of benefit. Whenever we find something that seems useful it will probably end up in RadeonHD within a couple of days of when we find it.

      Not sure about voltage adjust yet.
      Last edited by bridgman; 05 April 2008, 10:48 PM.
      Test signature

      Comment

      • puntarenas
        Phoronix Member
        • Jun 2007
        • 64

        #4
        Thank you

        Comment

        • alec
          Junior Member
          • May 2008
          • 46

          #5
          great news! Powerplay is last thing missing from open-source ATI drivers for me

          Comment

          • slacker
            Junior Member
            • Nov 2006
            • 73

            #6
            i dont see anything here: http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/
            Am i looking in the wrong place?

            Comment

            • agd5f
              AMD Graphics Driver Developer
              • Dec 2007
              • 3939

              #7
              Originally posted by slacker View Post
              i dont see anything here: http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/
              Am i looking in the wrong place?
              Add:
              Option "DynamicClocks" "TRUE"
              to the device section of your config.

              my powerplay stuff is available here:

              however, you can't dynamically change the power state at the moment as X does not provide a means to do so.

              Comment

              • pigah
                Junior Member
                • Sep 2007
                • 9

                #8
                Originally posted by agd5f View Post
                Add:
                Option "DynamicClocks" "TRUE"
                to the device section of your config.

                my powerplay stuff is available here:

                however, you can't dynamically change the power state at the moment as X does not provide a means to do so.
                Sorry to be dense, but this means there is not even a way to change it manually, i.e. at the commandline?

                Comment

                • agd5f
                  AMD Graphics Driver Developer
                  • Dec 2007
                  • 3939

                  #9
                  Originally posted by pigah View Post
                  Sorry to be dense, but this means there is not even a way to change it manually, i.e. at the commandline?
                  You can set the mode in your xserver config and it will stay as set until you change it and restart X. It's more of a proof of concept at this point. I'll be adding it to kernel modesetting where you will be able to change the settings on the fly using sysfs.

                  Comment

                  • piccolotux
                    Junior Member
                    • Oct 2007
                    • 29

                    #10
                    I'm actually using the latest git revision of xf86-video-radeon. The driver works beautifully. 2D performance are awesome and 3D is improving. Concerning powerplay options I'm unable to set any mode in my xorg config file. It seems that
                    Code:
                    Option "PowerPlayMode" "1,2 or 3"
                    is not recognized as a valid option. Am I missing something?
                    Thanks in advance

                    Comment

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