Display corrupt after upgrade 2006 iMac to Core 2 Duo

Discussion in 'iMac' started by mudflap, May 10, 2015.

  1. mudflap macrumors 6502


    Aug 24, 2007
    I've searched for hours on the web and in these forums for an answer but came up with nothing. Hopefully someone here has seen this before?

    I recently upgraded my 2006 20" 2.33gHz iMac Core Duo with 255mb ATI X1600 to a Core 2 Duo with the same clock speed. I'm handy and a quick learner but I admit this was probably a little over my head.

    I followed the ifxit guide and although I tore the LCD tape on the sides a bit and broke the optical drive fan cable connector (the black plastic tip that connects all 4 wires together disintegrated but I plugged each one back in to the connector on the logic board) but otherwise it turned out OK. I think.

    I turned the machine on, heard the chime and it booted back into Snow Leopard. However, I noticed immediately that something was wrong with the display. There were artifacts on the screen: colored lines through gradients; the Apple logo on startup had a white halo around it; white parts looked blue; and shadows under Finder windows didn’t blend into the background correctly depending on the background color, but usually had a white halo around where the shadow should be; and the entire screen had a magenta color cast to it.

    I installed a fan controller to monitor the temps, thinking I applied the thermal compound to the GPU incorrectly and it was overheating, but it hovered around 100° F and never got above 120° while watching 1080p video. But I remembered that the display artifacts started immediately on a cold startup so it couldn’t be heat.

    I repaired permissions, repaired the drive…nothing. I flashed my firmware to 5,1 and used MLPostFactor to install Mountain Lion 10.8.4 but the problem didn’t go away.

    So I thought I’d try to recalibrate the display to at least get it to a usable state. I removed the color casts using the Expert mode, and it looked a little better, and then by chance I toggled off the Native white point and BAM the screen looked perfect and all the artifacts disappeared! I toggled it on and off multiple times to be sure and each time with Native on the display became corrupted, then I turned it off and it was like brand new.

    I took a screen shot of the corrupted screen and emailed it to my other 2011 iMac and it looked fine, so I would think the problem must be happening after the GPU renders the screen and before it gets to the LCD?

    So now I’m wondering what caused this issue? Did I damage the display or display cable connector while taking apart the iMac?

    Sorry this was kinda long. Please let me know if anyone has ever seen this before or has any clue what happened.


  2. macthefork macrumors 6502

    Feb 2, 2013
    It sounds like from your testing that one of the the kernel extensions (kext) or drivers for the ATI X1600 may be incorrect for that combination of processor and video processor. The Core Duo is apparently a 32 bit processor. The Core 2 Duo is a 64 bit processor.

    (the following is taken from a posting on this site here)

    snip "...Whats not in 64bit is ATI1600Controller.kext, which is a big deal cuz it controls graphics card memory size, OpenGL and Quartz Extreme. Without that, the graphics is severely crippled..." End snip

    When you toggle the white balance off, it is probably going to the integrated graphics processor built into the new processor you installed and bypassing the ATI card. That's why it looks OK. Although the performance wouldn't be there, you could run it that way, or try to find a 64 bit controller kext. (that's unlikely, though) You may be able to boot into 32 bit mode in Mountain Lion to see if that helps.

    Try searching for ATI x1600 kext and see what comes up. There's a lot of posting on this issue.

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