Chosen Solution

After I installed Samsung EVO 860 SSD with OWC inline thermal sensor, I am having issues with hibernation. I can put the iMac to sleep the screen goes black, but I can still hear some faint fan noises. Trying to wake up from hibernation does nothing. I eventually have to hold down the power button to restart everything. This is what I have done which failed to solve it:

  1. SMC reset
  2. NVRAM reset
  3. PMSET Hibernationmode 3 and 25
  4. Clean Install of High Sierra with latest updates. I ran apples extended diagnostics and no error was found. My setup was fine until I upgraded my original HDD with Samsung Evo 860. Beside the wake up issues everything is running smooth. I am out of ideas, someone else had this issue?

Your systems firmware was designed to support the I7-2600 not the I7-2600K CPU The K version of the chip uses a different ID string and the system can’t leverage the ability to over clock this chip was designed to offer. Sadly you’ll need to swap out the CPU again with the correct one.