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JeffreySmith Level 1 (0 points)

Late 2006 iMac recently started to have constant freeze up issues and horizontal lines in display. From what I have read, the likely culprit might be a video card. But I noticed, when the iMac starts up in Safe Mode, the machine operates fine and with no random horizontal lines in display. My question, what system items related to display/video are not loaded in safe mode that is making this difference ?

iMac, Mac OS X (10.4.11)
  • den.thed Level 7 (26,017 points)
  • JeffreySmith Level 1 (0 points)

    Thanks for the link to Safe Mode info. And I realize Safe Mode loads certain extensions, but it was my observation during safe boot that my display did not have horizontal lines. My objective is to start machine in normal mode, disable problematic display/video extensions, and hopefully machine operates fine along with the proper display. I am trying to identify the display/video items/extensions to disable and should of worded my question differently.

  • WZZZ Level 6 (12,875 points)

    It's most likely not displaying those artifacts in Safe Mode because Quartz Extreme graphics is disasbled, only a bare bones graphics configuration. Probably not extensions related. More likely the GPU or GPU chip has failed. It might be the graphics drivers. For that you could reinstall, but it's usually not that.


    Safe Mode in Mac OS X v10.5 or later also disables Quartz Extreme (hardware accelerated graphics).

    You could try running the hardware test in extended, but getting a negative may not be all that meaningul, since it's not a great diagnostic. Might need to run several loops.


  • JeffreySmith Level 1 (0 points)

    This machine is running 10.4.11 so I don't know if Quartz Extreme is disabled in my safe boot. But, Is there a way to disable Quartz Extreme during normal startup?


    I ran the hardware test once without any problems found. I guess I should run the test again to determine if hardware related.

  • WZZZ Level 6 (12,875 points)

    According to that KB article, whether or not you have it, it won't be disabled in Safe Mode, so it's not that. Have you installed any non-Apple programs that would have placed extensions or made system modifications?


    Open Terminal in Utilities and copy/paste


    kextstat | grep -v apple



    Are you running any A-V? And yes run the AHT again in extended mode.

  • JeffreySmith Level 1 (0 points)

    While in Safe Mode, System Profiler reports Quartz Extreme is not supported, so possibly this might be an item of interest. But, from your earlier post, it sounds as though this is not extension related, and there is nothing I can do to disable Quartz Extreme in a normal startup, correct?

  • WZZZ Level 6 (12,875 points)

    But it reports it as enabled/supported when not in Safe Mode? If so, sounds like that article needs correcting. And you are certain you are running 10.4? What model iMac is this?

  • JeffreySmith Level 1 (0 points)

    Yes, Quartz Extreme is supported in Normal Mode. Not supported in Safe Mode


    IMac (Late 2006) 2 GHz Intel Core Duo, 10.4.11

  • WZZZ Level 6 (12,875 points)

    In that case, I think my original diagnosis is the most likely and that KB article is incorrect. Not for your OS, but here's someone who claims to have disabled it. You could do a search for "disable quartz extreme OSX"


    If you can do that, I don't know what effect that will have on graphics rendering where it will be needed. Sounds like you'll be running crippled. I'd make a backup before trying this. That's really all I know.


  • den.thed Level 7 (26,017 points)

    Those models had issues with lines on the display that required replacing the Display. There was even an extended warranty program that ran for a year or so after the Apple and Apple Care warranties ran out.


    From this point on it will only get worse and you will either start getting more line or the lines will turn into wider bands.


    You have several options.


    1. Replace the display. (which will cost more than the iMac is worth if you can find a replacement)


    2. Connect an external DVI or VGA monitor to it and disconnect the internal monitor.


    3. Buy a new iMac and sell that one on e-bay or craigs list for parts.

  • WZZZ Level 6 (12,875 points)

    Jeffrey, some years ago I was able to get Apple to extend the time on one of the repair programs by saying that I shouldn't be penalized just because my computer happened to last longer. The store denied my request, but I contacted Apple executive customer care, who authorized it. A major obstacle might be that they don't have those screens any longer.

  • WZZZ Level 6 (12,875 points)

    Den, I'm not finding a repair program for any of the early Intels, just the iMac G5s and the recent Seagate replacements. Do you have a link to that?

  • andyBall_uk Level 7 (20,490 points)

    there were a couple of recent threads in similar vein - removing the graphics driver kext(s) seemingly allowed a regular boot at the expense of slow/no graphics & 'dvd player app' not working. Needed to know what graphics chip the imac used, then the relevant files were removed. Far from ideal, and you should follow the good advice given already before pursuing that.

  • JeffreySmith Level 1 (0 points)

    Chipset Model: ATY, Radeon X1600.

    My first choice for action would be to remove kext(s) and see if this works. I read WZZZ's link to thread describing using Xcode and Quartz Debug and have not tried this yet.

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