Snow Leopard + iMac = hot GPU

Discussion in 'macOS' started by Cenobite, Sep 8, 2009.

  1. Cenobite macrumors newbie

    Sep 8, 2009
    Hello everyone,

    i have an iMac 20" (8,1), 2.66 GHz C2D, 4GB RAM and an ATI HD 2600 Pro graphics card. Whenever I run Snow Leopard the temperatures for the GPU are really high. The GPU Diode temperature is always around 70°C and after some time the CPU fan speed starts to increase to cope with the heat. As soon as I return to Leopard that temperature drops to around 60°C and the fan speed goes back to 1200 rpm (see attachment for screenshots of iStat Pro in Leopard and Snow Leopard).

    Here are some things I already tried/ruled out:

    • PRAM/SMC Reset: I did that countless times but did not help.
    • Bad installation/hard drive: I reinstalled Snow Leopard about 10 times using my internal drive, external drive and even using my MacBook to do the installation and then booting from it on my iMac. I also booted from my iMac hard drive with my Macbook using Target Disk Mode. It runs fine on the Macbook but on the iMac the temperature is still too high. I also reformatted the whole hard drive to force a rebuild of the EFI partiton.
    • Background processes/Spotlight: Nothing shows up in Activity Monitor or top in Terminal. Spotlight had also already finished indexing.
    • Bad RAM: I replaced my 4GB 3rd party RAM with the 2GB the iMac came with, no change.
    • Hardware conficts: I detached everthing except for the keyboard and mouse. I even did an installation that way.
    • Replace iStat Pro: Since iStat Pro was the only software that I installed after a fresh install, I used different applications to monitor the temperatures and make sure iStat isn't actually the culprit. Temperatures were still the same.
    • Log files: Nothing suspicious.

    Right now, I am out of ideas. Leopard runs fine on my iMac and even Snow Leopard works great except for this stupid temperature bug.
    I already called Apple hoping this to be a known issue but instead they told me they never heard of it before. They had me run a diagnostic program and send them the results but told me it will take a week to examine the data.
    I suspect that a bug in the ATI driver prevents the GPU from entering power saving mode. I attached my iMac to a power monitoring device and it uses around 10W more in Snow Leopard than in Leopard. But why does it happen to only a very few iMacs? I only found reports of 2-3 people having the same issue.

    Does anyone of you experience the same temperature increase or am I (nearly) the only one with this behavoir?

    Attached Files:

  2. scanflight macrumors newbie

    Sep 11, 2009
    Same problem as described

    Hello, I have EXACTLY the same configuration as you and my iMac shutdown on night due to hot temperatur after installing snow leopard.
    I just install Mac OS X 10.6.1 (10B504) but same problem.
    Here is my configuration:

    Jeu de composants : ATI Radeon HD 2600 Pro
    Type : Processeur graphique (GPU)
    Bus : PCIe
    Longueur de la voie PCIe : x16
    VRAM (totale) : 256 Mo
    Fournisseur : ATI (0x1002)
    Identifiant du périphérique : 0x9583
    Identifiant de révision : 0x0000
    Révision de la ROM : 113-B2250L-259
    Version du gestionnaire EFI : 01.00.259
    Moniteurs :
    iMac :
    Résolution : 1680 x 1050
    Profondeur de pixels : Couleurs 32 bits (ARGB8888)
  3. Cenobite thread starter macrumors newbie

    Sep 8, 2009
    We have exactly the same graphics card, even the ROM and EFI versions match. 10.6.1 didn't fix the issue for me, too. I had high hopes on the ATI Firmware Update Apple issued yesterday but couldn't install it because the installer told me I don't need it (and yet have to find someone who actually could).
    Unfortunately I still have no response from Apple. I called them yesterday and they are still elaborating on this issue. I keep you updated when I got any news from Apple.
  4. scanflight macrumors newbie

    Sep 11, 2009
    I found a new ATI patch but nobody can install it, due to this error message: "Cette mise à jour n’est pas nécessaire sur votre ordinateur"
    "= Alert: Your computer does not need this update"


    Some people with this problem too on this link:

    Very strange, a lot of people said hot temperatur with snow leopard...wait and see :cool:
  5. electroshock macrumors 6502a


    Sep 7, 2009
    I'd like to find an utility that will cause the 8600M GT in my mid-2007 MBP to burn out sometime before mid-2010 so that I can get it fixed under warranty on Apple's dime. :D

    All kidding aside, I never ran iStat before Snow Leopard, so I don't know how usage compares between the two versions. But I've certainly heard from others saying their GPU was generally running about 5-10 degrees C hotter in SL. Is that enough to worry about? I honestly don't know.
  6. Cenobite thread starter macrumors newbie

    Sep 8, 2009
    See my posting here. It seems that Apple only updated the Updater and not the firmware. 1.00.259 is the most recent right now.

    Most reports I've found are from people using mobile Macs. I'm not sure if the iMac problem only affects certain iMacs or is a general problem but people do not notice it, because the iMac is still rather quiet on higher fan speeds.

    It's not just the higher temperature but the consequences, like faster (and therefore louder) fans and higher power consumption. scanflight's iMac even shut down because of heat. I also can't use OpenCL as an excuse because the 2600 Pro is not supported. I don't see any reason to trade a cooler and quieter system in for nothing in return.
  7. ccrandall77 macrumors regular

    Jan 6, 2004
    Franklin, WI
    Same here

    I just noticed today that coming out of suspend, my iMac is at 65C. I'm looking at the smcFanControl status at the top of my desktop. I have the fan set to run at 1024rpm. I installed smcFanControl because I was getting a lot of problems with image persistence on the display.

    My iMac is an early 2008 alum, 2.8GHz C2D Extreme, 4GB RAM (aftermarket), and the ATI Radeon HD2600 Pro. Sounds like it's the same issue everyone else is having here.

    I recently installed Snow Leopard and I know that when running under Leopard that the temp coming out of suspend was usually around 29C. So 65C is considerably higher and has me very worried.

    Anyone found a solution to this yet? I've checked the Apple forums and so far I've found nothing.
  8. chinoamigo macrumors newbie

    Sep 19, 2009
    I have the exact same setup as ccrandall77 and I had the same problems too..

    When idling, my SL fan speeds:
    CPU: 1200 RPM
    Hard Drive: 2000 RPM
    Optical Drive: 2000 RPM

    The fans would speed up very quickly as a result of minor processes (like watching Youtube). This was fixed a bit in 10.6.1, but when I used Adobe lightroom, the fans would go bananas. What is ridiculous, is that the CPU fans wouldn't speed up, but the hard drive and optical drive fan.. they would reach speeds up to 5000-6000 RPM even though i was running CPU intensive programs off an EXTERNAL HARD DRIVE.

    I called Apple and they had no idea, suggested I take my setup to the Apple store (which I have yet to do... no time). So I just downgraded to Leopard.. Here are my fan speeds now:

    CPU: 1200 RPM
    Hard drive: 1200 RPM
    Optical Drive: 700 RPM

    As you can see, the hard drive idles at 800 RPMs less and the optical drive idles at 1300 RPMs less. Since I downgraded, my fans have yet to act up even while running the EXACT SAME programs. I laughed when the Applecare guy told me that this was normal.

    Anyways, hope they fix it soon...
  9. ccrandall77 macrumors regular

    Jan 6, 2004
    Franklin, WI
    Temporarily Fixed It

    I am running smcFanControl. I went in and adjusted the fans to run a little faster. Then I rebooted and everything was fine for the next couple of days. When it would go into sleep mode, my machine would get ice cold and the temp reading on the CPU was room temp upon waking.

    A couple days later, I found that after putting my machine to sleep a few minutes later it would wake up and EyeTV would have a window open with a TV show running. I killed the window and put it asleep again only for this to happen another couple of times. Finally, I just turned EyeTV off.

    After that, I saw the temps start to rise and stay hot even when the machine was supposed to be asleep. Again I messed with the fan controls (actually lowering them) and rebooted. For the next day and a half or so, it worked great. Now this morning it's hot again.

    I guess I should try removing and/or upgrading smcFanControl. As I write this, I'm realizing that if I were in Apple support this would be the first thing I'd try to eliminate as the culprit. I also have a lot of legacy apps on my machine from way back when I had a G4 iMac in Jan 2002. So, maybe I need to do some house cleaning of my libs and apps.

    Still, old apps and libs really shouldn't be causing this... esp when it ran fine under Leopard. In fact, under Leopard I needed smcFanControl to stop the LCD persistence I was seeing.
  10. Lymus macrumors newbie

    Jul 21, 2009
    power supply

    When I got my iMac back in May 2009 all was fine. Somewhere around the time I installed Snow Leopard I noticed the machine was getting a lot warmer. I found this thread and installed iStat. Normal temps were 65˚C for the GPU and 81˚ for the power supply. I took it to the Apple store (Cambridge UK) last week and they replaced the power supply, after conceding that it should run cooler. Results? Well, it's now running around 79˚ ...:confused:
  11. extralarge macrumors member

    Dec 15, 2008
    Hot mac

    Well, it's scaring when you're using the MBP for couple of hours. Your fingers even feel hot. I've seen two of the mbps were sent to repair for video card. Please, cool down....
  12. JoaoSilva macrumors newbie

    Sep 12, 2010
    Hot Imac And Fans At High Speed

    Hello i'm from Portugal, i have the same imac as you do , with exactly the same problem.
    When i made the upgrade to snow i started to hear the imac fans for the first time, until then they were so quiet.

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