Chosen Solution
I’ve just replaced the existing HDD (Samsung 1TB) with a SSD (Crucial MX100 512GB). At the same time, I’ve also boosted the memory going from 8 to 16GB. I also replaced the stickers around with the iFixit kit. Everything when fine, even though it was not easy work. On the first start, everything worked perfectly. RAM was recognized and SSD too. But after a couple of minutes, the fan started to go crazy and I honestly didn’t feel a great change in the way the iMac was performing. It did boot quicker though, but that’s mainly the only big difference. I’ve installed TG Pro to calm things down. The CPU temperature is not higher than 40°C and also the SSD drive (via SMART) announce a small 31°C. Everything is below 40°C in fact, manually setting the fan speed to 2000 rpm. At the same time, I see that kernel_task process is using around 70% of CPU load. I’ve read that it could be related to the fact the SSD drive is not “official” and not managed (temperature wise) correctly. How can I correct this ? Any idea ? Thanks in advance.
If I remember correctly the hard drive in these iMacs have a temperature sensor stuck on top of them with tape. When replacing the drive you need to keep that cable that sticks on the hard drive plugged in and just stick it anywhere with tape (on the SSD is preferred).
kernel_task issues are all over the map! It can be do to a physical issue within the system or an OS/App issue. As you replaced the primary drive after you’ve installed the OS and restored your backup the system needs to index the drive which is of course! Using the kernel_task! If you had a laptop you could have a bad SATA cable, kernel_task shows up again! If your laptop has a battery which is weak, yep! kernel_task again! If you have a misbehaving App or extension… and the list goes on and on. Let it run for a good day to let the system finish indexing then see where you are. Here’s a good write up on solving the issue within software: How to fix Mac’s kernel_task high CPU usage bug
