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I am struggling with an iMac 27" from 2011 with a Radeon 6970M GPU.

Without the nomodeset kernel parameter the display turns black when KMS kicks in.

With i915.modeset=1 radeon.modeset=0 the boot continues but the screen turns again black with a single _ in the top left corner when the display manager is started. Actually, the display manager is up and running and I can blindly launch a terminal and reboot the system.

I also tried to disable the discrete GPU as mentioned here by adding the following snippet to the GRUB config:

    outb 0x728 1
    outb 0x710 2
    outb 0x740 2
    outb 0x750 0

I furthermore played with the video=SVIDEO-1:d kernel parameter as mentioned here. Unfortunately, also without any success.

I am still facing the following issues:

  • graphics output only with nomodeset but then of course no hardware acceleration when decoding videos etc.
  • suspend/resume does not work
  • backlight control does not work - even when acpi_backlight=native is set as described here.

What bugs me is that Ubuntu apparently once worked on the iMac 12,2 as summarized here - at least suspend.

Any ideas how to resolve this issue?

ste
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0 Answers0