Vista interfering with MacOSX graphics via BootCamp

Discussion in 'iMac' started by nedzalife, Jun 2, 2008.

  1. nedzalife macrumors newbie

    Joined:
    Jun 2, 2008
    #1
    I'm new to the MacOSX platform and love it. Won't be going back to regular PC hardware unless absolutely necessary.

    I've posed this question in the Apple Support Forums, but the response I'm getting is from someone that doesn't seem to know what they're talking about.

    I have the newest fully loaded iMac (3.06Ghz, 4GB Ram, 8800GS video) and I'm having an issue with the GPU and bootcamp. Every time I'm in Vista, then reboot in OSX, the graphics seemed to be under-clocked in OSX. Its seems to be rendering at a power saver setting speed, so games and effects within OSX are slower (by as much as 75%).

    My assumption is that Vista's power settings profile is forcing the GPU to down-clock, but its weird cause this still happens if the profile in Vista is set to High Performance. The only fix I've found is to manually re-force the power settings by changing the power scheme in Vista to power saver or balanced, then force it back to High Performance, then immediately reboot back into OSX. Even if it's already set to the High Performance setting, re-forcing this power profile is the only way I can get the full GPU back when rebooting back into OSX. If you let the Vista OS sit idle for more than 5-10mins even on High Performance power scheme, then reboot, the GPU in OSX is underclocked.

    Does anyone know of a fix (even if it's command line) that will force the GPU back to full clock speeds in OSX in case I forget to apply this sudo fix before rebooting?

    Thanks!

    Hardware
    24" iMac (3.06Ghz)
    4GB RAM
    8800GS 512MB

    Software
    Issue occurred on 10.5.2 and is still occurring in 10.5.3
     
  2. AppleMatt macrumors 68000

    AppleMatt

    Joined:
    Mar 17, 2003
    Location:
    UK
    #2
    This is a very difficult and unusual problem. I'd strongly suggest filing a bug report with Apple, and enclose a system profile with it. They're pretty good at nailing down corner cases (or at least, I've found). To be honest, I'd be surprised if it were solved here.

    It looks like you've narrowed it down pretty well, but just to be sure, how have you obtained these numbers? Doing benchmarks or time-demos?

    Have you got the latest Boot Camp update/drivers installed in Vista?

    AppleMatt
     
  3. nedzalife thread starter macrumors newbie

    Joined:
    Jun 2, 2008
    #3
    Benchmarks are basically coming from World of Warcraft running in OSX. Ironforge will run at 160-220fps when the GPU is at full power, and 30-50fps when the GPU has been down-clocked by Vista's power scheme settings. Areas that usually fun 60-80fps (Sunwell) are crippled to 15-20fps.

    I'm not 100% sure about the latest drivers in Vista, the drivers that are installed are from the 10.5.2 OSX disc (for Bootcamp) and the latest GPU drivers from Nvidia. This seems like an ACPI setting that's being sent to the hardware, and OSX isn't resetting the hardware back to full spec during boot (like other *nix drivers normally do), so I don't know if a driver update on the Windows side would resolve this. I'm thinking the drivers on the OSX side need to be re-written to reset the GPU ROM back to full power during boot instead of assuming that it always is running at full power and that no other OS has interfered or imposed any settings on it. I could be wrong though. As I said, I'm new to apple hardware so I have little to no familiarity with how EFI differs from BIOS at the hardware level.

    Thanks for the tip, a bug report has been submitted. If anyone has experience the same thing I'd be interested in hearing about it.

    Thanks,

    Nedz
     
  4. AppleMatt macrumors 68000

    AppleMatt

    Joined:
    Mar 17, 2003
    Location:
    UK
    #4
    You seem to have quite a good understanding of the problem. The only thing I could possibly suggest is holding 'Command + Option + P + R' during your first reboot (into OS X, before the computer 'chimes'). This resets the PRAM and VRAM, which includes power management settings. I'm not confident that this will solve it however. After that, I cannot immediately think of anything.

    Good luck!

    AppleMatt
     

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