Mid 11 Temp sensor problem causing lag of performance

Discussion in 'iMac' started by lakriz, Nov 9, 2013.

  1. lakriz, Nov 9, 2013
    Last edited: Nov 9, 2013

    lakriz macrumors newbie

    Sep 12, 2013
    Now i have searched the web a few months about my graphic performance problem on my 3,1ghz 2011 iMac.. The 6970 1gb card has absolute no power in OSX.. but works perfect in windows..

    I have a fan speed problem caused by the ambient temperature sensor which is not present in the list of sensors in all temp sensor programs..
    I understand that this missing temp information is causing the SMC to tell OSX to slow everything down.. Fair enough.. Everything works in windows so i guess windows doesn't get the info to slow down .. But i hate windows..

    I have tried change the ambient temp sensor.. but still no success.. If i reset the SMC the ambient temp comes up with 128c reading.. i guess that is a "faulty mode" value..

    Every thing points at the logic board.. Witch is very expensive.. (buy another iMac 2. hand instead!!) Yeah.. But I'm a fighter.. Everything else on the computer works fine..

    Would it be possible somehow to cheat the SMC -> OSX info transfer of temp values.. or faulty mode.. ?

    And can someone confirm my problem by trying to disconnect the ambient temp sensor and describe their iMacs behavior ?

    I keep my fans down with "macs Fan Control".. works perfectly.. If i close the program, CPU and Optical fan run max speed.

    But i have still no graphic performance.. (games runs very bad even in very low settings) and iTunes album scrolling is crappy

    Any ideas?

    /Kristian, Denmark
  2. Gurpartap Singh macrumors newbie

    Jun 9, 2010
    Hi Kristian,

    I have the same issue with my 2011 iMac 27''. Were you able to fix the Ambient Temperature Sensor?
  3. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

    Aug 5, 2001
    What is your definition of "Games run very bad"?
  4. Gurpartap Singh macrumors newbie

    Jun 9, 2010
  5. lakriz thread starter macrumors newbie

    Sep 12, 2013
    Hey there.. Yeah decreased fps.. feels like old games them I turn off gfx acceleration and use software acceleration..

    But no i didnt find a solution.. I bought a 250gb sad and installed win 7 on half of it.. and play diablo and borderlands2 from windows.. and i must say windows runs VERY smooth on a mac.. :)

    To get rid of the fan noise i use Macs Fan Control.. works both in windows and OSx.. And works fine adjusting the fan speed in games.

    Its possible to buy a used main board from TheBookYard.. but still expensive.. I guess the only solution is to replies the main board / logic board.

    Let me hear if you find a solution.. Next time I just replaces the 1tb hard drive with a ssd.. i never use 1tb anyway.. Then i don't harm the main board..
  6. omvs macrumors 6502

    May 15, 2011
    When I busted my 27" internal lcd cable, I had similar reduced performance in OSX. But it got a *LOT* better if I had two external monitors hooked up - maybe not to normal levels, but definitely better. I think the GPU goes into a different power savings mode in that case, because my gpu idle power triples with two displays hooked up, even when the sensors work.

    Since your internal display actually works, hooking up just a single external display might have the same effect in OSX....
  7. lakriz thread starter macrumors newbie

    Sep 12, 2013

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6 November 9, 2013