Apple Event: May 7th at 7 am PT
I have a considerable difference between cpu temp and cpu heatsink temp im my early 2008 imac. The cpu can be 70-80 degrees C while heatsink stays at 50. Imac also seem to slow down cpu when hot. Causing 'top' to show high acerage. Has the cpu lost some of it's thermal contact with the heatsink?
Could this be fixed by just replacing the thermal paste between cpu and heatsink.
iMac (20-inch Early 2008), Mac OS X (10.7.3)
Sorry for the typos: top shows high average load when cpu gets hot
Also the cpu fan does not seem to spin up very much (~1200 rpm) when cpu gets hot.
You are right, 20 C is a pretty big temp difference if they are supposed to have good thermal coupling. While the temp of the cpu is still acceptable, well below 100-110 C, might be worth talking to an Apple service tech and see if it is even possible to inject thermal compound between the cpu and heat sink. Since the cpu is soldered in place that may not be possible to do.
Hi
thanks for your prompt answer
I did read zif socket for the cpu in some spec for this imac model, but dont remember where.
Also, I was hoping for the possibility to loosen the heatsink from the top of the cpu w/o having to take out the cpu itself.
Sadly machine is just 2 weeks out of its 3 year applecare plan, so i was thinking of doing this myself.
Any experiences on this out there?
I probably have the wrong iMac model link (as bookmarked for mine), but this site has lots of illustrated procedures for what you are talking about.
http://www.ifixit.com/Device/iMac_Intel_20%22_EMC_2105_and_2118#deviceGuides
I presume you are using something like iStat Nano to monitor the temps. I guess you could also try (as a quick fix) something like SMC fan control where you could up the rpm's on the CPU fan. (which is what I currently do on my late 2006 iMac).
Thanks for the link. the heat sink layout looks a lot like on my 2008 iMac.
So you are experiencing the same differences in temp between the cpu and it's heat sink?
Yes i am using iStat nano.
Increasing the fan RPM does lead to colder heatsink, but the the problem is that my cpu does seem to live it's own life temperature-wise
Seems like there's no way around going in and replacing the thermal grease, and making shure there is a good thermal connection.
Not noticed the same problem. My iMac keeps freezing, which after much research does seam to be a potential problem with the graphics chip over heating.
The heat sink difference between my CPU and heat sink in my 2007 macbookpro varies from about 10 deg to around 16 deg. I guess as others have said, 20 deg is quite a worrying difference.
I've just installed fan control on the MBP, and it's stablised that temp difference to about 12 deg. I've never really checked on it before.
Big difference between cpu temp and cpu heatsink temp im my early 2008 imac
