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User profile for user: fixiefoo735
fixiefoo735 Author
User level: Level 1
4 points

Late 2012 iMac 27” high CPU

Okay, so I recently received this iMac with 32gb of RAM and a 2.12gb fusion drive. Comes with a 2gb graphics card and a quad-core i7 processor. The first thing I did was reset the computer and I downloaded the OS on the ssd. Now every time I open up an app like FaceTime or discord, my cpu spikes and kernel_task runs through the roof. Is this something to do with my hard drive? Or maybe the thermal paste around the cpu?? It gets frustrating as this slows down everything on my Mac. As soon as I close everything out, the cpu levels drop from about 98% to 2% for just one app. The computer doesn’t make any weird noises

iMac 27″, macOS 10.15

Posted on Oct 22, 2020 3:37 AM

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User profile for user: John Galt
John Galt
User level: Level 10
141,332 points

Posted on Oct 22, 2020 5:26 AM

Given the symptoms as well as the results of your actions you took to address them the second and fourth bullet points below are applicable.



Please read If kernel_task is using a large percentage of your Mac CPU - Apple Support.


A runaway kernel_task can be due to a number of factors, such as:


  • a failed or disconnected temperature sensor
  • cooling system inefficiency (an inoperative exhaust fan on Macs so equipped, possibly clogged with dust, including the heat sink)
  • a worn out, missing, or non-Apple (user-installed) battery on portable Macs
  • similar hardware-specific causes including internal hardware additions or modifications, external USB and other connected devices, or the driver software required to use them.


If you can find no other explanation for its behavior, an SMC Reset is justified: Reset the System Management Controller (SMC) on your Mac - Apple Support.



The computer doesn’t make any weird noises


I would expect the fan speed to audibly increase: bullet point #2. Investigate that possibility. Apple Hardware Test will exercise an iMac's exhaust fans and readily identify an inoperative one.

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User profile for user: John Galt
John Galt
User level: Level 10
141,332 points

Oct 22, 2020 5:26 AM in response to fixiefoo735

Given the symptoms as well as the results of your actions you took to address them the second and fourth bullet points below are applicable.



Please read If kernel_task is using a large percentage of your Mac CPU - Apple Support.


A runaway kernel_task can be due to a number of factors, such as:


  • a failed or disconnected temperature sensor
  • cooling system inefficiency (an inoperative exhaust fan on Macs so equipped, possibly clogged with dust, including the heat sink)
  • a worn out, missing, or non-Apple (user-installed) battery on portable Macs
  • similar hardware-specific causes including internal hardware additions or modifications, external USB and other connected devices, or the driver software required to use them.


If you can find no other explanation for its behavior, an SMC Reset is justified: Reset the System Management Controller (SMC) on your Mac - Apple Support.



The computer doesn’t make any weird noises


I would expect the fan speed to audibly increase: bullet point #2. Investigate that possibility. Apple Hardware Test will exercise an iMac's exhaust fans and readily identify an inoperative one.

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Late 2012 iMac 27” high CPU

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