Temperature & Fan Speed (noise)

Discussion in 'iMac' started by drthom, Jun 16, 2017.

  1. drthom macrumors newbie

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    Jun 10, 2017
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    USA
    #1
    I am a new member of MacRumors threads and pretty much an iMac rookie, so feel free to ignore me and/or tell me where I have run amok.

    I am interested in buying a fancy new iMac very soon, and I'd like to make an intelligent, experience-based choice. Noise and temperature are two of my main concerns.

    It seems that, relevant to these issues, there are 5 different 27" iMac models:
    #1 - 3.4 i5, RP570
    #2 - 3.5 i5, RP575
    #3 - 4.2 i5, RP575
    #4 - 3.8 i5, RP580
    #5 - 4.2 i7, RP580

    I would appreciate it if new 27" iMac purchasers would post their experiences -- specifying their iMac configuration, task performed (gaming, editing, whatever), and component statuses (CPU & GPU temperatures and fan speed).

    I would love to order the i7 model (#5 above), but it would be useless if it were noisy.

    Thanks!
     
  2. fokmik macrumors 68000

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    #2
    i7+580 is loud and gets hot quickly, we have again the same scenario we had with the M295x
     
  3. Trebuin macrumors 65816

    Trebuin

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    #3
    I have #5 & it will be noisy unless you use something like "turbo boost switcher pro" to disable hyper threading. That drops it to #4 & drops the power used, saving your electric bill a little bit. I haven't played much with the video card yet.
     
  4. Chancha macrumors 6502a

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    #4
    I am more interested if throttling would kick in for #5 like it did with 2015. If higher noise means better cooling methods for consistent performance then I am okay with it. Don't think I will push the machine 24/7.
     
  5. macdoofus macrumors member

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  6. Quash macrumors regular

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    Sep 27, 2007
    #6
    Tom's hardware has a really nice article on these Kaby Lake chips.

    CPU \ Intel thermal utility \ Stressed (realistic) \ While gaming
    i5-7600 (3.5) 73W \ 49W \ 42W
    i5-7600K (3.8) 103W \ 64W \ 55W
    i7-7700K (4.2) 137W \ 98W \ 77W

    This should gives a reasonable indication how much heat needs to be dissipated by the CPU.
    i5-7600 clearly has the best balance between power(noise) and performance.
    Only get the i7 if you know you need it. Or don't mind fan noise.

    Personally i wish you could get the 580 with the non k cpu's.
    Because the performance difference on stock speeds between both i5's is so small it doesn't matter at all.

    The video cards should be closer in wattage but it still should make some difference.
    The cores in the 575 are clocked a little bit slower compared to the 580 i think. (based on the TFlops)
    And the clock speed of the 570 is even slower than the 575. Plus there are of course less cores to power.

    My guess is that #2 should be the best blend of power versus performance. If you need more performance you will have to tolerate more noise or/and higher temps. #1 will use even less power but if it has better performance per watt is hard to tell. Unless you buy em both and do all the benchmarks in a similar environment. Doubt anyone is gonna wanna do that ;)
     
  7. Trebuin macrumors 65816

    Trebuin

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    #7
    I used Unigine Heaven to stress the video card & I couldn't get the temps to go over 75 with or without hyper threading. I'm used to the video cards going up in the 90s but it looks like this one runs really cool...or I need to find a better burn in utility.
     
  8. fokmik macrumors 68000

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    #8
    i think any combo with both i5 will come with no fan noise in almost any conditions...i have the 7600k+580
     
  9. Quash macrumors regular

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    Sep 27, 2007
    #9
    Unigine Heaven doesn't load the CPU much. If you run stuff that taxes both the GPU and CPU fully things will get interesting. Something like Wow even though it's an ancient game can stress both the CPU and GPU. Combine that with long playing time. That's a recipe for disaster. Killed 2 of our iMacs in the past. (+ our social life but that's another story ;) )
    --- Post Merged, Jun 16, 2017 ---
    Maybe but burning 25 extra watts for close to no performance gain is not a great idea imho.
    These K cpu's are meant for overclocking in big towers preferably with big coolers..
     
  10. fokmik, Jun 16, 2017
    Last edited: Jun 16, 2017

    fokmik macrumors 68000

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    #10
    yea but with the 3.5" i couldnt get the 580 and that extra vRAM so is the only way
    but like i said, no fan noise, i never got the fans to spin over 1600rpm and no temp higher than 90C
    i even tried a game at the request of someone under macOS nothing, under bootcamp the fans was louder with 1800rpm...i dont know why since i tried the exact game with the exact settings
     
  11. Quash macrumors regular

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    Sep 27, 2007
    #11
    True as can be, still doesn't make it a great idea by apple to put these K chips in an iMac..

    But why do you need 8GB Vram specifically?
    For 99% of the games the performance difference between 4 and 8 is not percievable.
    Of course the extra GPU cores and higher GPU clock of the 580 will help performance.
    Unless you are dead set on doing VR on your iMac. For that the 580 is required i believe.
     
  12. Trebuin macrumors 65816

    Trebuin

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    #12
    If you run Prime95 on the CPU alone, it'll go right over 100. If you're looking at CPU & GPU use at the same time...I'm assuming you're rendering with both CPU & the GPU since that's pretty much the only thing that could drive both to max. If you're just gaming...you can shut off the CPU & suffer a minor impact (Cinebench drops from 125 to 115 for me) while the fans don't run.
     
  13. fokmik macrumors 68000

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    #13
    i dont game, i only play league of legends thats all...but i need for photoshop some rendering graphics projects and i will start in VR project and the extra power and vRAM is a must have for me
     
  14. Trebuin macrumors 65816

    Trebuin

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    #14
    If it's a must, then be like me & put up with the fan speed.
     
  15. fokmik macrumors 68000

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    #15
    neeh im ok with the i5 and 580 :)
     
  16. Quash macrumors regular

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    #16
    That's nice to know, what do you use to manage your CPU under MacOS?
     
  17. Trebuin macrumors 65816

    Trebuin

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    #17
    Turbo Boost Switcher Pro...but that won't be enough to stop something like prime95 from maxing out the CPU...it's too good. I usually watch the CPU clock down on intel power gadget, but that's not compatible with this processor. I need to find another utility for that. & I use a fan speed manager.
     
  18. drthom thread starter macrumors newbie

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    #18
    Thanks, everyone.

    So, from posted results, it seems that I should either avoid the "K" CPUs or find utilities that can "throttle down" the CPUs to some reasonable rates.

    Apple apparently has not engineered an effective cooling system.

    Are the ventilation slots just above the memory access door in back "intake" or "exhaust" for the cooling system? Maybe some sort of DIY blower/sucker fan could solve the problem.

    Thom
     
  19. Neo999955 macrumors newbie

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    Jun 13, 2013
    #19
    I'm very surprised the fans run even when doing non-intensive tasks.

    How loud is it when streaming Netflix, for instance, on a 27" i7? We do a LOT of that in our room on the Mac.
     
  20. Luxtrau macrumors member

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    Jun 16, 2017
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    Germany
    #20
    Don't worry, I think it's not that aweful. When doing things like video streaming fan is running, but at lowest possible rpm. It's very quiet, any kind of sound can drown fan noise.

    PS. I have an 27 iMac
     
  21. propower macrumors 6502a

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    Jul 23, 2010
    #21
    I already have the i7 with 580 coming...
    Questions...
    - When doing non stressful things is the fan at the lowest speed?
    - Is it pretty quiet there?
    - For more intensive things has anyone used xcode to turn hyperthreading off? Any better?
    - Again for more intensive things - has anyone turned Turbo off? Any better?

    I am an audio guy and want to have the full BW available but only need it 10% of the time. 90% using the i7 in non-hyperthreading mode and Turbo off - with lets say constant 50% load on the CPU - very light GPU use- would be sort of a max point. Would the fans on the i7 stay at minimum there?
     
  22. jayfromnova macrumors newbie

    jayfromnova

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    Northern Virginia
    #22
    That's the combo I am leaning towards. Are you saying that the fan noise is not bad then? I think I've ruled out the i7 because of fan noise, and now it's about the GPU choices. Your observations are much appreciated.
     
  23. jerwin macrumors 65816

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    Jun 13, 2015
    #23
    It's the exhaust port.
     

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