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2011 iMac 27" Overheating? (playing Crysis)

S

Sunday Ironfoot

macrumors regular
Original poster
Apr 14, 2011
215
389
Recently bought a 2011 iMac 27", it's a top end model with i7 3.4GHz CPU, AMD 6970M 2GB, 16GB. I went with an SSD only (no hard drive).

I think it might be overheating. Whenever I play Crysis, after a while the game's frame rate will slow right down to sub 5fps levels, then back up again to 30fps+, and it will do this at regular intervals (about every 10 seconds). I've also noticed this happening during a 3D Mark 2006 benchmark run. I read somewhere that this could be due to the GPU overheating, where the GPU will rapidly downclock itself to a very low MHz, then back up again once its cooled down a bit.

Some observations:

  • This happens when the room is quite warm, I'm in quite a small room and gets hot when the iMac has been running for a while (also had this problem with a dual GPU PC).
  • It takes a while for the slowing down/speeding up to kick in, probably after room has warmed up.
  • The problem is alleviated if I open a window/door to let the room cool down.
  • The problem is alleviated if I fix Crysis' frame rate to 30fps.

Is this a known issue with the iMac? Will I just have to put up with overheating when it's under stress (playing games etc.), finding ways to keep it cool? Is the top end iMac's hardware is at the absolute limit of what the cooling system can cope with?

On the plus, I am impressed with the performance, I have Crysis running at 2560x1440 +2xAA and with everything on High or Very High. :)
 
Last edited:
Can you hear the fans spinning up at all when the system is under load?

You can use an application called SMC Fan Control to set a higher minimum fan speed. Try and keep the fans spinning at RPMs in the same proportions of each other, i.e. if you increase one fan by 2x increase all of them by 2x.
 
rj86 said:
Can you hear the fans spinning up at all when the system is under load?

You can use an application called SMC Fan Control to set a higher minimum fan speed. Try and keep the fans spinning at RPMs in the same proportions of each other, i.e. if you increase one fan by 2x increase all of them by 2x.
Click to expand...

I can definitely hear the fans spinning up, although they are still relatively quiet compared to a high powered tower desktop PC say.

I've noticed that air gets pumped out of the two slits around the back near to top, although more air comes out of the right slit than the left slit, is this normal?

SMC Fan seems to be for OSX but I'm playing Crysis in Windows 7, is there a Windows fan control equivalent?
 
Sunday Ironfoot said:
SMC Fan seems to be for OSX but I'm playing Crysis in Windows 7, is there a Windows fan control equivalent?
Click to expand...

You set the fan speeds in the OSX side and then reboot into Windows 7. The fan speeds you set are remembered when you are running Windows 7. Good little program as you can set profiles such as Gaming - it also won't allow you to reduce the fan speeds below the Apple's minimum settings.
 
Sorry, should have realised you were in Windows and explained better.

I haven't tested it personally but I was under the impression that as the fan control is set in the SMC (System Management Controller) it would be persistent if you boot into a different system after setting it in OS X. Might be a bit annoying if you want to use Windows for anything other than Crysis though with the blowers whining away :p

Not sure if there is a Windows equivalent for setting this on a Mac, unlikely.
 
rj86 said:
...it would be persistent if you boot into a different system after setting it in OS X. Might be a bit annoying if you want to use Windows for anything other than Crysis though with the blowers whining away :p
Click to expand...

Will it let me set the min/max speeds? If I leave the min speed alone but just increase the max speed, would that work?
 
Yes, that's the right one and I don't know/think so for the other question...
 
My 2010 iMac critically overheats during the final boss-fight with settings on Medium. The fans blaze away but it's no good - my machine always craps out.

This is the reason why I've not finished Crysis!
 
would lowering the res and details helps generating less heat? I know it will look crappy but may be it will be enough to get pass it? I don't have a copy of Crysis but I would love to try it on mine...
 
Sure, mate. I've considered it. But there's another issue - the end of the game is rubbish, and I'm not sure I can be bothered with it!
 
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