Hazelnut
10-24-2016, 07:27 PM
Please forgive the rant. Please feel free to ignore the remainder of this post and move on.
I have a 2012 iMac. the iMac12,2 model. 27 inch display. It has never given me a problem until last week.
First, it decided it liked to show me a few light green vertical lines. Then it decided to show me a LOT of them. For the benefit of anyone who would like to see, it looked a lot like this but more evenly spaced:
https://macman860.files.wordpress.com/2013/02/gpu.jpg
The system also decided that fully booting was no longer an option. Even safe boot was a no-go. Fortunately, I had updated the bios (a few years ago) so the system supports Apples over-the-internet diagnostics and install.
Diagnostics gave me a lovely cryptic error-code of 4MOT/4/40000003/HDD-1242 (the 1242 changed with each re-run of the test). Apple's knowledge base was less than useful. Forum posts and Google searches were inconsistent. But I did learn a few things:
The error code indicates a failing hard drive.
The Green lines are associated with a failing GPU (known issue in some 2011 models)
Someone else managed to diagnose and correct the issue as bad RAM.
With all of those lovely options, this is going to be hellish.
First off, a hard drive problem is unlikely to cause the green lines issue unless it made just the right alteration to something in the graphics subsystem. Very unlikely. A video card issue shouldn't cause the system to fail to boot (especially since it was getting past POST). I know it wasn't booting all the way because it never got as far as talking to the DHCP server.
An overheating video card might cause the system to halt. And I suppose it is possible that it could cause the green lines issue if the heat is causing the video RAM to corrupt. So, leave it off overnight and try in the morning. No-luck.
RAM test time. Despite the fact that Apple's diagnostics tested the RAM it was spitting out a hard drive error and not making any mention of RAM issues. Fortunately for me, the system had 2 sticks of RAM. Also, fortunately, it doesn't actually matter which one is inserted where. So, pulled the first one, re-ran diagnostics. Same error, same green lines.
Pulled the second one. No green lines. Same diagnostics results. Rebooted into install/recovery. Ran disktool, fixed a bunch of errors. Rebooted as normal. System is fine (except only have half my normal RAM). I will re-run the diagnostics but I'm busy posting this.
I have a 2012 iMac. the iMac12,2 model. 27 inch display. It has never given me a problem until last week.
First, it decided it liked to show me a few light green vertical lines. Then it decided to show me a LOT of them. For the benefit of anyone who would like to see, it looked a lot like this but more evenly spaced:
https://macman860.files.wordpress.com/2013/02/gpu.jpg
The system also decided that fully booting was no longer an option. Even safe boot was a no-go. Fortunately, I had updated the bios (a few years ago) so the system supports Apples over-the-internet diagnostics and install.
Diagnostics gave me a lovely cryptic error-code of 4MOT/4/40000003/HDD-1242 (the 1242 changed with each re-run of the test). Apple's knowledge base was less than useful. Forum posts and Google searches were inconsistent. But I did learn a few things:
The error code indicates a failing hard drive.
The Green lines are associated with a failing GPU (known issue in some 2011 models)
Someone else managed to diagnose and correct the issue as bad RAM.
With all of those lovely options, this is going to be hellish.
First off, a hard drive problem is unlikely to cause the green lines issue unless it made just the right alteration to something in the graphics subsystem. Very unlikely. A video card issue shouldn't cause the system to fail to boot (especially since it was getting past POST). I know it wasn't booting all the way because it never got as far as talking to the DHCP server.
An overheating video card might cause the system to halt. And I suppose it is possible that it could cause the green lines issue if the heat is causing the video RAM to corrupt. So, leave it off overnight and try in the morning. No-luck.
RAM test time. Despite the fact that Apple's diagnostics tested the RAM it was spitting out a hard drive error and not making any mention of RAM issues. Fortunately for me, the system had 2 sticks of RAM. Also, fortunately, it doesn't actually matter which one is inserted where. So, pulled the first one, re-ran diagnostics. Same error, same green lines.
Pulled the second one. No green lines. Same diagnostics results. Rebooted into install/recovery. Ran disktool, fixed a bunch of errors. Rebooted as normal. System is fine (except only have half my normal RAM). I will re-run the diagnostics but I'm busy posting this.