GPU Power Management - (GTX 5xx/6xx)

Discussion in 'Mac Pro' started by Cuyahoga, Sep 27, 2012.

  1. Cuyahoga macrumors member


    Jun 12, 2007
    I suppose this applies to any unofficial GPU, but in my case, I'm referring to a GTX 570 (1280GB).

    Question: I'm wondering how you can monitor and/or control the GPU's power state on Macs not using the AGPM kernel extension (AppleGraphicsPowerManagement.kext).

    Example: The GTX570 is capable of running at 3 distinct power states (Gstates). Users used to be able to edit AGPM to modify when exactly to switch between Gstates 0, 1, & 2. I'm under the impression that this is no longer necessary, but in my case (MP 3,1) there was never an AGPM.kext to begin with.

    Why do I care? I'm afraid my GPU isn't optimally switching between power states. Comparing the MP's total power consumption between 10.8.1 & XP, XP draws more power running the same task (e.g. Unigine benchmark). Granted, it's not really the same task, and it's presumptuous to deconvolute changes in total power. But when playing a game in XP, it'll consistently be about 380-400W with smooth performance, while in OS X, it fluctuates much more, but rarely exceeds 300W. Unigine though will stay between 350-370 in OSX. Portal 2 will be at 200+ fps, but still stutter.

    Thanks so much!
  2. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    When AGPM is not called up, the PC BIOS power states shoud still control card.

    I have mentioned this many times, but it does;t seem to stick.

    Mac video cards say "Hi, I'm a xxx" to the system at boot via EFI, but once the driver loads the cards run via their PC BIOS. When my dad put a 20 MB Winchester HD (Yes, I meant 20 MB) into his PC, it booted to the same PC BIOS system. It is a sad reality, but Apple gave up on cards that ran purely via EFI after just one try, the ATI X1900XT. And even then they had to cheat and put the PC BIOS into the firmware for the Mac Pro so that the card would work in Bootcamp.

    In short, every GPU since then has had boot screens via EFI, but most of cards function is defined via PC BIOS. Embarrassing but true.

    To verify that card switches power states, you can run GlView and watch as card goes from a score in 100's to score in 1000s in first 3 seconds of running benchmark.

    Nvidia isn't full of idiots. Those guys wrote drivers that deal with PC BIOS cards perfectly. Our EFI cards are a touch better, but the power management is run the same either way.

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