Underclock iMac GPU

Discussion in 'iMac' started by jimmy43, Jun 22, 2012.

  1. jimmy43 macrumors member

    Joined:
    Apr 9, 2008
    #1
    Hey guys, I have a 7,1 iMac that runs extremely hot. The GPU temps reach over 80 C. It will eventually crash and shut down. We took it apart and tried to clean it up and see if there are any issues, but it's still too hot.

    smcFanControl helps a bit, but I'd like to be able to underclock the GPU a bit so that it doesn't get into those critical temperatures.

    I looked around the net and there is only the ancient ATIcelleratorII.

    I had an idea, what if use a Windows utility to change the GPU frequencies, and then switch back to OSX, would those stick, or are they software only?

    Any other tips are also appreciated.

    thanks
    T
     
  2. Razorhog macrumors 65816

    Razorhog

    Joined:
    Sep 16, 2006
    Location:
    Arkansas
    #2
    Did you verify that all fans are operating correctly? Under what circumstances does it heat up like that? Are you gaming?
     
  3. jimmy43 thread starter macrumors member

    Joined:
    Apr 9, 2008
    #3
    Yes I have fan control software that is monitoring the Fan Speed and Temperatures. I have set minimum Fan speeds to somewhere in the middle (eg, CPU fan is at 3000rpm), because setting it to MAX makes the computer extremely loud.

    So the fan speeds are "maxed" out. Idle temperatures are around 70C, under load, like watching a YouTube Video, its 75C-80C.

    My understanding is that this is very high, it shoudl be below 60C at most.

    Hence I'd like to underclock the GPU. This computer won't be getting used for anything too intense like gaming, so it's ok.

    thanks!
     
  4. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #4
    Those temperatures are normal for a 7,1 iMac. I've never seen mine anywhere close to 60C or below when idling. The GPU in mine can get up to 80C with no problems. This is still within ATI/AMD's specs for the GPU's used in the 7,1 iMacs.
     
  5. jimmy43 thread starter macrumors member

    Joined:
    Apr 9, 2008
    #5
    Thanks Intell, that's good to know. I am thinking of handing this over to my mom though, so I wanted to make sure it doesn't break down on her randomly.

    If possible, I'd still like to underclock the GPU, so do you think Underclocking it in Windows, would change the hardware clock (and hence be underclocked in MAC), or is that software only?

    thanks
     
  6. Razorhog macrumors 65816

    Razorhog

    Joined:
    Sep 16, 2006
    Location:
    Arkansas
    #6
    In that case his problems might not be heat related after all.
     
  7. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
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    #7
    The Windows underclock is a software clock set and is removed when the machine is restarted. What kind of crashing does it do?
     
  8. ivoruest macrumors 6502

    ivoruest

    Joined:
    Jul 12, 2010
    Location:
    Guatemala
    #8
    It seems like you may have a heat sink problem on your Mac. I do know that iMacs tend to run quite hot, but having crashes is a symptom of throttling or just protecting the CPU from melting. Still I just can't understand how 80°C is your max temperature. My Macbook Pro gets around 90° when on extreme loads.

    You should take it to an Apple Store or an authorized repair shop. Maybe they can tell you whats wrong.

    My possibilities:
    -Dust accumulation
    -Heat Sink problems
    -Fans not working correctly.
     
  9. jimmy43 thread starter macrumors member

    Joined:
    Apr 9, 2008
    #9
    Thanks for your help guys.

    According to the person who used this computer it would crash while doing intensive tasks (Photoshop or something). It was already taken to a repair shop where they said it needs a new video card ($800?) and so they gave it to me to try to fix for free.

    Too bad about the windows thing, but thanks for the info.

    Maybe reapplying the thermal paste on the video card would help?
     
  10. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #10
    What kind of crash/freeze does it do? Does the screen freeze except for the mouse cursor?
     

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