Chosen Solution

So i have an iMac 2011 21inch that originally came with intel i5 2400s CPU, decided to upgrade to i7 2600cpu, even though it takes 95w of power instead of 65, people say its possible to do this upgrade on this machine. So, i followed guide on ifixit on how to change cpu and i assume i did everything very accurately. Upon first start, i hears usual startup chime, a screen backlit flashed on and off and then heard fans working hard but black screen. Held power button until it turned off and tried again, this time same scenario but no backlit flash - screen completely dark, heard start chime with optical drive sound and fans working hard. Im pretty sure its not the backlit turned off but something else. Checked all display connectors and they connected properly and are tight. Also tried the command option p r combo, i do hear iMac restarting a lot of times as long as i keep holding the combination. Once released - it supposedly boots up. Any suggestions? Put old cpu back?

I would put back the original CPU to see if all is good again. I am not sure the logic board can handle 95w. That is a lot more than 65w. I had the same issue with 2010 iMac i3 upgrading. Even if the CPU fits physically you can as everymac.com writes: “…one only can upgrade the processor in an Aluminum iMac with a socket-compatible processor that has the same, or lower, TDP as the originally installed processor.” So it can be that the BTO i7 model has different specs. I searched but could not find anyone that successfully upgraded the 2011 iMac 21.5" from i5 to i7 CPU. Of course there can be reasons for the fans blowing,

  • the CPU temp cable is loose
  • the LCD temp cable or other cables are loose

I tried almost exactly the same thing. I switched out the original i3-550 with an i7-870 - but I got the exact same black screen on boot. I hear the fans start but the screen never comes on. I’ve tried everything I can think of to no avail. My understanding after some research is that the New processor has to match or be below the processor TDP (thermal design power) So the i7-870 has a 95W TDP - but the 2010 iMac only supports up to a 74W TDP processor. That being the case, the best processor you could upgrade a 2010 iMac to would be the i5-680. However, my understanding is also that the 2011 iMac supported an i7 processor in one of the original Apple configurations - and therefore most likely has a higher TDP support than the 2010. You might be able to get something more powerful into the 2011.

Hi guys, I did upgrade from i5 2400 to i7 2600 for my 2011 IMAC 27" , they are both 95 TDP based on my research, however, after the installation, the screen went to black when I was trying to power it up, and after around 10 seconds, the fans were running on full speed without stop. And the screen kept black. Anyone knowing how could this still happens when the CPUs are at the same TDP?? And I have known that someone has successfully upgrade from 2400 to 2600 with no such problem what so ever. Really need some help here. p.s. I also added a SSD used OWC cables and upgraded to 16G RAM, but I don’t think these upgrade could cause the above problem as I have replaced the original RAMs back and also unplug the SSD which I added, but still not working……please help!!!