27 inch iMac 775M/780M, i5/i7 quad -- loud when gaming?

Discussion in 'iMac' started by MythicFrost, Nov 13, 2013.

  1. MythicFrost macrumors 68040

    MythicFrost

    Joined:
    Mar 11, 2009
    Location:
    Australia
    #1
    Hey,

    Just wondering if anyone who has a 27 inch iMac w/ the 775M or 780M and the i5 or i7 quad, can tell me if it's loud when gaming at all?

    Cheers
     
  2. yjchua95 macrumors 604

    Joined:
    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #2
    Well, since I play it in an air-conditioned basement (it's mounted on a VESA there), it's pretty quiet still.

    Mine's a 3.5GHz i7, 32GB RAM, 4GB GTX780M and 512GB SSD.
     
  3. reery macrumors regular

    reery

    Joined:
    Sep 18, 2012
    #3
    I've got an iMac 27" i5 and 775M.

    Temperatures while idle are around 25-30°C and while gaming around 55-62°C.
    The fan stays at its 1200 rpm rendering the device silent except if you have a hard drive you'll hear that drive spinning.

    Even while rendering or using 100% CPU it won't bother the fan.
     
  4. MythicFrost thread starter macrumors 68040

    MythicFrost

    Joined:
    Mar 11, 2009
    Location:
    Australia
  5. Nazmor macrumors newbie

    Joined:
    Oct 16, 2013
    #5
    All depends on type of game, imac configuration and apparently luck. I don't know 775m so I will just say about i5 and i7 with 780m. If game is cpu intensive then your cpu will start heating up before gpu, otherwise your gpu will speed up fan. Both cpu and gpu are cooled by the same fan. There is very characteristic fan profile used by apple that will try to keep fan in low revs until almost very end thermal limit, so in general if one of cores will reach 95degC then fan will quickly speed up, sometimes full speed will not be enough and core will reach 99degC and start throttling ( lowering MHz ). This can happen if you do cpu benchmarks or play cpu intensive games. Which game will stress your cpu I cannot say, from my experience for example guild wars 2 will be cpu intensive in wvw but gpu intenive in solo leveling areas. Also bf bc2 may heat up your cpu, more likely i7 than i5 though and this is a second issue: i7 will generate more heat than i5 so from my observations there is around 5-10 degC difference ( possibly because of hyperthreading) and it may be enough to break 95degC limit when fan will start increase speed from base 1200 rpm. So if you want to just play games possibly i5 is a better option. If you however go for i7 and you will play games that would stress your cpu then you can use simple trick using power management profile and set max cpu usage to 99% which will disable turbo boost so cpu will stay at 3500mhz and it will lower very significantly temperature so the fan will not have to work that hard.

    Second problem is gpu overheating, 780m will start increasing fan speed from around 82degC and will go full speed at around 86-87degC. This will be more gradual than cooling cpu.

    Because cooling cpu and gpu is combined then if one is overheating then fan will speed up which will cool down both so if game will use a lot of gpu then fan may go to 1800rpm and airflow will also help cooling cpu.

    Last thing is luck or cpu lottery. I got i7 with second core usually getting 7 degC hotter than fourth core so second core usually is overheating first even though other cores still have some room. Then I got replacement i5 and this one was great, all cores much cooler with very low differences around 2degC but...gpu was overheating much easier than in the first imac and in the end fan was working much harder comparing to the first one.

    Just you have to remember that imac is really a laptop with a big screen, there is no space for proper cooling, and apple set fan profile to limit noise as long as it is possible, in typical "gaming pc" cpu will never reach 99degC, will never throttle, max maybe 70degC, but ... In "gaming pc" you have 4-5 fans working all the time and in imac there is just one with base speed 1200rpm, very quiet at that speed but can get noisy at max 2640rpm.

    All blizzard games work great, diablo 3 fan at minimum 1200rpm all the time, in Starcraft i7 may occasionally increase fan speed to 1600rpm which is still quite quiet, for warcraft with i7 I would suggest disable turboboost which does not have impact on framerate and keeps fan at lowest speed.

    Hope it helped. All testing has been done in bootcamp windows 8.1.
     
  6. MythicFrost thread starter macrumors 68040

    MythicFrost

    Joined:
    Mar 11, 2009
    Location:
    Australia

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