rip & diannee,
My solution got me through a period of multiple daily kernel panics and freezes, but I ultimately didn't see enough of an improvement to justify disabling the graphics features. I do still use it, but only when I have to have a reliable computer running all day.
The procedure I describe in the posts above did help, but gradually there seemed to be little difference between Quartz On or Quartz Off, so I stopped running Quartz debug by default and now only use it when needed. As the crashes started coming back and getting worse, this is what I did to keep my 3-1/2 year-old iMac running:
- I disassembled it down to the logic board and cleaned everything thoroughly and then reinstalled the OS.
- I run fsck -fy every time it freezes or crashes.
- ! run Disk Utility Repair Permissions daily.
- When not using the computer I logout, even if for 30 minutes which helps keep it cooler.
- Run smcFanControl with the fans set to 2200.
- Added an external fan to the back of my iMac sucking hot air out of the top left hand vent area (my left facing the screen) running constantly.
- I try to logout every 3 hours and take a break to keep it cooler.
- Run Diskwarrior from boot to repair the file structure when the crashes come too often.
The fan thing I came up with here:
http://hints.macworld.com/comment.php?mode=view&cid=124345
This seems reasonable to me that part of the issue is air is not flowing efficiently inside the system when the graphics card is running so hot. This seems like a defect to me given that so many users have this same issue with the same basic models and graphics configuration.
The next thing I was going to do was to disassemble my iMac again and do as you did, reapply the thermal paste to the graphics chip, but that solution appears to have mixed success. Still, that's my next step along with making a bracket for fans I can tape to the upper vent, a bank of out-sucking fans instead of just the one. If heat is the issue which it appears to be, as summer approaches it's just going to get worse, so I need more airflow. The concern that is that more air means more dust, so ideally I should also probably make some kind of fine filter for the bottom vents that allows good airflow, but keeps out the nasties.
I wish Apple would step up and do a recall on this MMX chip/logic board. It's not normal wear-and-tear, it's a DEFECT and Mac buyers deserve a little more support and a logic-board recall on this issue from Apple. I still hope for Apple to do the right thing here.
For now though, the out-sucking fan does seem to help a bit but it's not enough. If I have Dreamweaver, Bridge, Photoshop, Espresso, Transmit, Mail, Safari, Pandorajam2, Splashtop2 and various other utilities running, I can expect a crash within about 3 hours, so I am trying to manage the hardware I have until I can replace the logic board which, I _hope_ will solve it, but I'm not sure that it will, so I'm reluctant to drop $400-500 on a questionable, used logic board and graphics card in an attempt to fix a computer that ought to be working without me wondering when the screen is going to go crazy and freeze or panic. A new replacement board is as much as a new iMac, so used is the only real option.
I have always felt that Apple products were reliable enough and Apple support flexible enough to work with Apple support and apply logic to these sorts of issues and they just got taken care of. But now it seems that in order to protect what is a significant purchase from Apply you MUST buy Applecare to supplement the basic warranty. If you don't it's a real crap-shoot as to whether or not your Mac will outlast your buddy's Dell and that is a sad state of affairs in my own personal Apple fanboi-land here in Atlanta!
JoeL
Atlanta, ga
