Excessive GPU heat when using a second display

Discussion in 'iMac' started by ashleyw, Nov 20, 2011.

  1. ashleyw macrumors newbie

    Nov 20, 2011
    Without a monitor connected (via Thunderbolt/mDP) to my iMac (2011, 3.4 GHz, 6970M 2GB), iStat Menus reports the GPU is using ~15 watts, and has a temperature of 60c. With one connected, it uses ~35 watts, and is ~80c. Both of these are when idling.

    Regardless of it pushing an extra 1920x1200 monitor, 80c seems very excessive. I use my computer near enough everyday for up to 10 hours, and I'm worried about the long-term stress due to such a high temperature. Running Battlefield 3 for hours on end doesn't exceed ~65c!

    Is this normal behaviour for displays via the Thunderbolt port, and if so, is it safe long-term?

    (SMC reset, fans working correctly, no dust in air ducts, etc.)
  2. marsmissions macrumors 6502


    Jan 5, 2010
    Washington, US
  3. ashleyw thread starter macrumors newbie

    Nov 20, 2011
    Even 10 hours a day, 6 days a week? I know it's in the 'safe' zone, it'd shutdown otherwise, but it still feels too high. Like I said, running Battlefield 3, a very GPU heavy game, doesn't even hit 70c, never mind 85c! :eek:
  4. lamboman macrumors 6502

    Aug 13, 2011
    You'd be surprised. GPUs are designed to handle a lot of heat, with most having limits around the 100-105C range. Ridiculously high, I know.

    You should be fine. The system has been designed to last, as has the laptop graphics card inside it (which is actually going to be running cooler in the iMac than in a laptop most of the time).
  5. Spike88, Nov 21, 2011
    Last edited: Nov 21, 2011

    Spike88 macrumors 6502a

    Jan 25, 2010
    Couple of tricks to keep its insides cooler...

    They are:

    A - Remove its under belly memory plate. This allows more air flow into the bottom of the screen. Simply unscrew the memory plate and keep in a safe spot. One doesn't see this under belly area anyway. I've done this on my iMac.

    B - Install SMC Fan Control software and "increase" its 3 x fan speed by 300 RPMs. Thus, ensure more air flow directly on its inner GPU area. No worries, 300 RPMs faster isn't that much. If wondering, I run the inner fans 300 RPMs faster (then suggested factory default) within my iMac and it runs great. Nice and cool - where I want it. re: http://www.macupdate.com/app/mac/23049/smcfancontrol

    C - Another trick is to place a "super silent" 8" 110V fan behind the screen and blow air against the back of the screen. Get the fan with its own 3 x speed settings. This helps as well.

    Yes, one might be within the upper "SAFE ZONE" of inner heat range. But making it cooler (into lower end of safe zone) is much better in the long run...


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