Weird checkerboard pattern after crash

Discussion in 'iMac' started by aphorist, Feb 22, 2013.

  1. macrumors newbie

    Jun 12, 2008
    Hi everyone,

    A few days ago, my iMac froze on the screensaver. I hard rebooted it. When it started back up, there were vertical stripes on the screen, even over the Apple logo on the startup screen. Then it went to this checkerboard pattern:

    Figuring it was a bad video card, I made an appointment to take it to the Apple Store. But today I tried booting again, and it's working fine.

    This is a mid-2011 20.5" iMac running 10.7.5. It could be a coincidence, but these issues started shortly after I installed AirPort Utility 6.2 and Digital Camera RAW Compatibility Update 4.04 via Software Update.

    Do these issues seem familiar to anyone?

    Attached Files:

  2. macrumors 6502


    Sep 23, 2012
    Really odd, sounds like an overheating/dieing video card, but the fact that the timing coincides with a software update could say otherwise.
    Try watching temps using SMCFancontrol. ;)
  3. macrumors member

    Aug 6, 2008
    Did you add aftermarket ram? My 2012 iMac exhibited these same symptoms. I had Apple take a look. They indicated that all of their testing pointed to incompatible Ram. After I switched to Crucial ram I haven't had an issue with freezing since. However, my display recently started showing bright white spots in the bottom left hand corner. The spots are constant. Apple is replacing my unit with a new one.
  4. thread starter macrumors newbie

    Jun 12, 2008
    Thanks for the suggestions, lucasfer899 and hummer28.

    I installed SMCFanControl. I'm not sure what a normal temperature is, but it's currently showing 37 degrees C, or 98.6 F, which doesn't sound bad.

    No, I haven't upgraded the RAM yet. It's stock everything. Glad your iMac is still under AppleCare, hummer28!
  5. macrumors newbie

    Jan 6, 2013
    I actually just had this happen this morning. Was listening to Pandora and playing Fieldrunners in Chrome when it happened. Noticed I was nearly maxing out the CPU and checked my temperatures 30 seconds before it started to flicker and they seemed a bit high.

    First the screen started to flicker, then I got a number of artifacts on the screen. Music continued to play for 20 seconds before it locked up. Restarted and I have artifacts across the Apple logo. It boots after cooling down, but after 10 seconds of logging in starts all over again and reboots again.

    Going to assume the video card is on its last leg. Fans are running ok, but 2 months ago when I was installing a new HD in it I noticed the Video card had some discoloration on it. Had hoped it would last a bit longer.

    This is on my 2008 24" iMac with nVidia 8800 GS.
  6. thread starter macrumors newbie

    Jun 12, 2008
    Well, It's been a few days and I haven't seen this issue again. I'm doing regular backups, so I guess I'll just wait and see. I wouldn't be surprised if the video card gives out before too long, but maybe it was a fluke (fingers crossed)...

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