GPU Heat

Discussion in 'iMac' started by niklasios, Nov 9, 2014.

  1. niklasios macrumors newbie

    Joined:
    Oct 23, 2014
    #1
    The new iMac retina, maxed out, will make a lot of noise and heat even watching a simple movie in fullscreen
    All the fans will turn on, cant imagine doing more intesive gpu things

    Hope this get fixed somehow....
     
  2. azure247 macrumors 6502

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    Sep 9, 2008
  3. GGJstudios, Nov 9, 2014
    Last edited: Nov 10, 2014

    GGJstudios macrumors Westmere

    GGJstudios

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    May 16, 2008
    #3
    There's nothing to fix. It's normal for a Mac to get hotter during intensive workloads. If you're not already doing so, use iStat Pro (free) or iStat Menus ($16) to get accurate readings of your temps, fan speeds, etc., rather than relying on your sense of touch or sound. A forum member has posted a copy of iStat Pro that has been "tweaked" to enhance compatibility with recent OS X versions. You can download it here.
    The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat. CPU Tjmax = 105C (221F), GPU Tjmax = 100C (212F) on i3, i5, i7 processors. (Source: Intel)
    Unless there is a rare defect in a Mac, most temps are well within the normal operating range, considering the workload being put on it. Websites with Flash content, games and other multimedia apps will put higher demand on the CPU/GPU, generating more heat. This is normal. If you're constantly putting high demands on your system, such as gaming or other multimedia tasks, expect temps to rise and fans to spin up accordingly. It's just your Mac doing its job to maintain temps within the normal range.
    It is also quite normal for your Mac to become extremely hot to the touch during intensive operations. The aluminum body transfers heat more effectively than other materials used in computer casings, so you will feel the heat more. This doesn't indicate that it's overheating and will not harm the computer to be hot to the touch.
    The fans in Macs are always on when the Mac is on, spinning at a minimum speed which varies by Mac model. They will spin faster as needed to keep temps at a safe level. If your fans are spinning up without increased heat, try resetting the SMC. (PRAM/NVRAM has nothing to do with these issues, so resetting it will not help.)
    The intake and exhaust vents are in the back of the computer near the hinge on all Mac notebooks (except the new MBP with retina display, which has intake vents along the sides at the bottom). The iMac vent is on the back of the computer. Make sure the vents remain unblocked to allow your computer to perform at its best. For Flash-related issues:
     
  4. rainydays macrumors 6502a

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    Nov 6, 2006
    #4
    Yes it's normal for it to get hotter during intensive load. But it's not normal for the iMac to get THAT hot. The 295x and 4GHz i7 will both throttle under heavy load and the fan will blast away at the highest speed. This indicates that the iMac clearly isn't built for components that powerful.

    Now do the same with a 2013 i5 iMac. Yes the fans will speed up a little but not all the way, and it will not start throttling down the processors. That's how the iMac was designed to work.
    The fully loaded RiMac has components in it that it clearly wasn't designed for. The cooling system is not adequete for it.
    Will it hold up? Who knows? We'll see in a couple of years.

    Your description of the iMac cooling system is outdated by the way. Time to do some catching up. :)
     
  5. jbuk1, Nov 10, 2014
    Last edited by a moderator: Nov 10, 2014

    jbuk1 macrumors member

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    Oct 24, 2014
    #5
    The fact the fans spins up means it's clearly designed to deal with the heat.
     
  6. Crunch macrumors 6502

    Crunch

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    L.A. (although currently overseas)
    #6
    The reason for the M295X rating up the fans is its thermal envelope. The standard GPU, the M290X has a TDP of 100W, whereas the M295X has a TDP of a whopping 250W!
     
  7. joema2 macrumors 65816

    joema2

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    Sep 3, 2013
    #7
    The 250W TDP number is wrong. The peak power consumption of the entire 4Ghz retina iMac under full load is only 288W. How could just the GPU be pulling 250W?

    http://support.apple.com/en-us/ht3559

    The Radeon R9 295X2 dual-GPU board pulls 500W and comes with a liquid cooler. A single chip R9 295X would pull about 250W. Maybe that's where the 250W number comes from, but that is *not* what's in the retina iMac.
     
  8. Crunch macrumors 6502

    Crunch

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    L.A. (although currently overseas)
  9. GGJstudios, Nov 10, 2014
    Last edited: Nov 10, 2014

    GGJstudios macrumors Westmere

    GGJstudios

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    May 16, 2008
    #9
    False. First, you claim it's not normal for the iMac to get THAT hot, but you have no idea what temps are involved, because the OP didn't specify. Second, you have no idea whether the fans spinned up because of increased load on the GPU or the CPU, or even specifically which processes were putting the workload on the system. You don't know if temps were anywhere near the throttling range and you don't know if the fans were spinning at full speed. Your assumption that the iMac isn't built for the components inside is evidence of your lack of understanding.
     
  10. steve23094 macrumors 68000

    steve23094

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    Apr 23, 2013
    #10
    The R9 M295X is only available in the Retina iMac at the moment, so you wouldn't call it a specialized version it's the reference.

    GPUBoss is just outright wrong. You will note that it says the specs are 'Rumored', they were posted a long time ago before anybody knew anything concrete about the M295X. For example the GPU clock is wrong [source: http://arstechnica.com/apple/2014/10/the-retina-imac-and-its-5k-display-as-a-gaming-machine/]. It's also illogical that GPUBoss scores the M290X 7.5 out of ten and the M295X 6.6.
     
  11. rainydays macrumors 6502a

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    Nov 6, 2006
    #11
    No it doesn't. It just means that the fans spin up in order to deal with the heat. It doesn't mean that it's doing an adequate job at cooling it down.

    ----------

    Having now had first hand experience with the fully loaded RiMac has confirmed my assumptions that the iMac isn't built to handle the heat of the 4GHz i7 and the 295x.
    Put heavy load on either one of them, the fan will start blasting at full speed and the processor start to throttle.

    It is so very clear that the cooling system of the iMac (which is amazing by the way) doesn't do an adequate job at cooling these components. If it did it would not start throttling so early on.
    Compare that to the Mac Pro which is clearly designed to handle heavy load and still keep things cool and quiet.
     
  12. GGJstudios macrumors Westmere

    GGJstudios

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    May 16, 2008
    #12
    Yes, it does. If the fans were not able to keep the heat within the safe operating range, your Mac would automatically shut down.
    You have no evidence that it's throttling. Fans spinning faster is not evidence of throttling. They spin faster to avoid it. Apple obviously knows much more than you do about what is required to handle the heat generated by the iMac components. Just because you put a heavy workload on it and the fans spin up does not mean it's not functioning well, as designed.
     
  13. tom0511 macrumors member

    Joined:
    Nov 1, 2014
    #13
    A max. GPU-temperature of 105° C is at least something to think about.

    From my (limited) manufaturing knowledge: Leadfree SMT soldering processes run in the 280° - 300° temperature range in the oven, so solder joints basically should not be something to worry about.

    The PCB surface and the multiple copper layers should also stand that heat, the PCB laminate normally burns in the 360°+ range. Also no worries here.

    105°C. is a typical breakpoint for max. operating temperature in component specifications. There are higher grade specs available, but at a higher price though. Not sure what component specs Apple is using here, but running system components at the edge of specifications over a longer period of time is something which might affect the time-to-failure calculation.

    Taking those thoughts into account, there might be issues on the long run if you mainly use your riMac for tasks, which drive CPU and GPU to the edge.

    But as no one knows how the components in the imac are being specified, this is really just guessing.

    Apple Care should be a no-brainer option in the riMac anyway.
     
  14. 5iMacs, Nov 10, 2014
    Last edited: Nov 10, 2014

    5iMacs macrumors regular

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    Oct 25, 2014
    #14
    Mixed in with a lot of hysterical speculation, there's been some measurement and analysis of throttling in this forum.

    The i7 spikes quickly to 100C on sustained load (a Handbrake job) and throttles at 3.8 GHz. It's well known that Haswell CPUs will do that as automatic thermal protection. There's nothing mysterious about this, notebooks do it all the time.

    The fact that the i5 peaks out at 86C under the same load (and somewhat less throughput due to lack of HT) without bumping the fan past its default of 1200 RPM is a useful distinction.

    The M295X is a little harder to characterize because games and benchmarks create different kinds of load, although it's notable that on the most punishing ones like Unigine Valley ExtremeHD the fans rev pretty high and the FPS difference compared to the M290X is negligible.
     
  15. FredT2 macrumors 6502

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    Mar 18, 2009
    #15
    I did the testing to show the throttling with the i7. Is the result you're talking about a Handbrake test as well? Are there any comparisons that show time difference between the i5 and i7 running Handbrake? Does the i5 throttle at all? Can you point me to such a test? Thanks.
     
  16. 5iMacs macrumors regular

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    Oct 25, 2014
    #16
    Yes FredT2, you were the source, and I much appreciate the contribution of actual numbers to the discussion. :cool:

    I'm not near my i5/M290X iMac to offer the plateau clock speed for the Handbrake run, all I have in my notes is the fan speed (1200) and the temperature (86C). As I've announced before it's just not possible to spike the i5 past 86C. I'll get back to you on that clock speed later.

    I do have one other oddball stat, that it's about 15% faster than my old 4.2GHz Sandy Bridge i5 box, which I thought was kind of cool.

    For relative speed I've found the Geekbench multithreaded score to be pretty good guide, but I'm up for a throughput test if we can arrange it. Do you know of some substantial downloadable content that we could use for a 10 minute encode test?
     
  17. joema2 macrumors 65816

    joema2

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    Sep 3, 2013
    #17
    The problem is there's been a lot more of the former than the latter.

    Professional testing has given a more balanced perspective. Under high simultaneous CPU & GPU stress, Mac Performance Guide described the fan noise as "reasonable and tolerable": http://macperformanceguide.com/iMac5K_2014-stress.html

    In each of the below tests the 4Ghz retina iMac with M295X was faster than an 8-core new Mac Pro with dual D700s:

    http://macperformanceguide.com/iMac5K_2014-createImageSeries.html

    http://macperformanceguide.com/iMac5K_2014-CaptureOnePro-raw-to-JPEG.html

    http://macperformanceguide.com/iMac5K_2014-UnigineValley.html

    http://macperformanceguide.com/iMac5K_2014-Cinebench.html

    http://macperformanceguide.com/iMac5K_2014-video-transcode4K.html
     
  18. 5iMacs macrumors regular

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    Oct 25, 2014
    #18
    Thanks joema2, those are some really useful and credible benchmarks. Although I'm starting to think these Unigine Valley numbers should come with a little bit of an asterisk, I mean, how useful is a benchmark that rates the M290X, the M295X, and dual D700s with approximately the same FPS? Other benchmarks paint a pretty clear picture of an average of 20% benefit for the M295X on games, and close to 50% more on OpenCL stuff.
     
  19. rainydays macrumors 6502a

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    Nov 6, 2006
    #19
    "Reasonable and tolerable" is so very subjective. Why is no rpm value stated?

    This is however not the result I got when I pushed the i7. The fan was blasting at full speed and not at all reasonable and tolerable by my measures.
    I guess this could either be a case of better thermal paste application on his cpu or a cooler ambient temperature (mine was about 23C).
     
  20. GGJstudios macrumors Westmere

    GGJstudios

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    May 16, 2008
    #20
    Why is no rpm value stated?
     
  21. rainydays macrumors 6502a

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    Nov 6, 2006
    #21
    2600+ rpm

    (most of the time between 2610-2643)

    ----------

    Yeah, and the GTX 775M I tested it on this weekend beat them both with 23.5fps.
     
  22. GGJstudios macrumors Westmere

    GGJstudios

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    May 16, 2008
    #22
    While that's high, it's not full speed, as others have reported 2700+ rpm under heavy load. Have you checked your specific temps?
     
  23. jbuk1 macrumors member

    Joined:
    Oct 24, 2014
    #23
    I hope I can help clear this up some more with some screen shots.

    iMac as per signature, m295x.

    Running drivers I downloaded this week from AMD website (14.20.1002.1002-140716a-174376C.)

    I've just had another hour of playing bf4 on 3840 × 2160 at ultra settings.

    Measured GPU before and after and before was 59 degrees after was around 84 degrees.

    Screen shots as promised. http://imgur.com/a/sJQc2
     
  24. FredT2 macrumors 6502

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    Mar 18, 2009
    #24
    Try this: go here and download the HD .MP4 (1280x710) version of the video. Then do a conversion using the AppleTV 2 preset. You might want to also run it using the AppleTV 3 preset if you want a longer run. I'd appreciate if you could do this before tomorrow.

    https://vimeo.com/109762295
     
  25. Charlemagne macrumors newbie

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    Oct 25, 2008
    #25
    Cool benchmarks. Interestingly though. the author of these returned the iMac (http://macperformanceguide.com/blog/2014/20141103_2226-iMac-goes-back.html).
     

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