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I have a late 2009 27" iMac which has served my well for many years. Unfortunately, it seems the graphics card is broken. Trying to boot normally, I just get the grey screen of death after the initial chime and Apple logo. First of all I tried all the usual resets, including:

  • Safe boot
  • Boot into recovery (including Internet Recovery)
  • Re-install OS from OS X DVD
  • Clear NVRAM
  • Reset SMC

Results:

  • Booting into recovery mode works (CMD+R) with mayor graphical glitches.
  • Trying to run the Apple Hardware test (D) results in the same grey screen of death as the on normal boot.

Thanks to the tips from Boot hangs on grey screen (even when booting from USB drive with fresh OS X install) I de-activated the graphics card by booting into single user mode CMD+S on boot and moving the driver files:

/sbin/fsck -fy /
/sbin/mount -uw /
mkdir /dsle
cd /dsle
mv /System/Library/Extensions/ATI* .
mv /System/Library/Extensions/AMD* .
touch /System/Library/Extensions
exit

After this OS X normally boots up into OS X again, so I guess the graphics card is broken.

Under About this Mac > More Info ... > Graphics/Display the graphics card is still shown correctly:

ATI Radeon HD 4850:

Chipset Model:  ATI Radeon HD 4850
Type:   GPU
Bus:    PCIe
PCIe Lane Width:    x16
VRAM (Total):   512 MB
Vendor: ATI (0x1002)
Device ID:  0x944a
Revision ID:    0x0000
ROM Revision:   113-B9110C-425
EFI Driver Version: 01.00.383
Displays:
Display:
Resolution: 2560 x 1440
Pixel Depth:    32-Bit Color (ARGB8888)
Main Display:   Yes
Mirror: Off
Online: Yes
Display Connector:

But even with the graphics card de-activated, there are graphic glitches.

enter image description here

Dose this mean the OS is still running of the dedicated graphics card? Or dose this mean the error is somewhere else?

  • The "boots normally" part is confusing. Please clarify: With driver in place your different attempts result in what? The picture displays boot without drivers? Which system version is this? What is shown under System Information > Graphics/Displays? – LangLangC Jan 12 '18 at 16:19
  • Give it a run through Apple Hardware Test. Then give us a shout when you get the resulting error code. You might have to put in the install disk that it came with to get the diagnostics to work, but it usually doesn’t need it. – bret7600 Jan 12 '18 at 18:48
  • Put the graphics board in the oven.... mine had it, and works since 3 years after 200° treatment – user2707001 Jan 12 '18 at 23:29
  • Added additional information to the original question! – wowpatrick Jan 13 '18 at 10:27

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