Chosen Solution
Initial Issue: I’m trying to fix my iMac. It will not boot to any kind of device or partition. It will startup and chime, and it will show the progress bar, which will then freeze about halfway through indefinitely. Things I’ve Tried: Booting to recovery When I do this, it just shows that progress bar, and will freeze again. Booting to external diagnostic drive I have a Mac Diagnostic drive that I tried to boot to. (Note that the boot options do appear) When booting, it will show the loading indicator spinning for a couple minutes then freeze. NVRAM Reset Did the NVRAM Reset and am getting the same results. Target Disk Mode Used target disk mode to see the drive on another Mac and verified the disk. Different RAM Lastly I tried different RAM and still I’m getting the same issue. Booting to Hiren’s Boot CD Tried to boot to a Hiren’s Boot CD just to run a disk check, but it will sit at a black screen with a blinking text indicator Booting to Ultimate Boot CD Tried to boot to an ultimate boot CD. Surprisingly it booted, however I noticed some items were horribly misspelled, and had random symbols in it. (Weird) When navigating to any option, either the CD, or the keyboard and mouse would freeze entirely. Additional Notes: I really want to avoid doing a OS reinstall. Seeing as booting to my diagnostic drive didn’t work either, I don’t think that would help at all either. If the logic board is shot I can probably replace it, but obviously that would be more of a last resort. I really don’t have any other ideas. If anyone could help it would be appreciated.
I think you’ve given me enough clues to identify the problem. Sadly, your dedicated GPU board has failed. The clues that tell me: Intel graphics engine is working (Target Disk Mode) you see the Icon on the screenYou see odd symbols and other artifacts when booting up off the disk Here’s the replacement part you’ll need: ATI Radeon HD 2600 Pro w/256 MB - Apple P/N 661-4426 You should also get thermal paste and thermal pads to remount GPU board to the heat sink. Here’s one source: ATi Radeon HD 2600 Pro 256 MB
