Replaced CPU with i7, now 1 LED blinking I replaced the Core i5 2.7 GHz CPU in my iMac 27-inch (mid 2011) my with an i7 2600.

On boot I got a blinking single LED on LED1. Reading up that normally means insufficient power. The main fan would spin cycle up and down.

I put the i5 back in and it boots fine. Things I'm not sure about:


I'm assuming the CPU is good, but can't be 100% sure
I didn't put the RAM back in when I tested the i7, but normally you'd get a long tone.


Anything else I can try? I'll have another go when I've got more time and double check I've seated all the cable correctly etc.

Big shame if it doesn't work - I was looking forward to the upgrade!
Ok - so I took it all apart again. Reseated the i7 CPU and it all booted fine. 

Runs like a champ! Awesome upgrade :-)