I found myself in a particularly nasty place yesterday. I had followed advice given to me by an Apple engineer and either what they told me to enter in terminal was wrong, OR, I mistyped. Either way the result was a iMac that would not boot and gave a kernel panic at every grey boot screen. I tried resetting the PRAM/NVRAM via command-option-P-R, I tried booting from single user mode, booting to safe mode and booting from the DVD to bypass the HDD. None of these worked and all resulted in the kernel panic.
So i call Apple care and the guy there was fantastic and he determines a fried logic board and happily gives me a case number to have it repaired under warranty. Now I have been a Mac user for long enough to know that you don’t (Most of the time) go from working fine to rebooting and having a fried logic board. So I racked my brain and spent hours on Google and I am happy to say I fixed it, and I will share with you what the issue was and how I fixed it in the hope it may help many others in the future.
Now for reasons I won’t delve into I have an EFI Firmware password set on my Mac. I presume if your reading this article your the same. The EFI firmware password essentially stops you doing any of the important key combinations at boot, resetting PRAM/NVRAM, single user mode the whole shebang. Now this is useful in many many circumstances except when your screwed like I was. Essentially when I thought I was resetting my PRAM and NVRAM I was doing absolutely nothing. If your as screwed as I was and cannot get to a DVD to boot OR you have forgotten your password there is only one way around it.
- Add or remove a stick of ram. Obviously if you have one stick in, add one and if you have two in remove one.
- Power on the mac and immediately press and hold command-option-P-R.
- The system will restart with the ‘bong noise’, allow it to do this 3 times. On the third ‘bong’ you can let go of the keys.
- The machine will now boot with a cleared password and reset PRAM/NVRAM.
- You can shut down the machine and replace the original ram configuration.
I hope this helps anyone that was in as much hot water as me! Good luck