Unable to boot Ubuntu 20.04 on iMac 12,2 (i7, Mid-2011) without kernel option `nomodeset`

ste

1/9/23, 7:01 AM

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?

0 + 1

mac

kms

radeon

xserver

20.04

guiverc

1/9/23, 7:06 AM

You weren't specific as to which 20.04 ISO you were using; given it's old hardware - did you try an ISO with the GA kernel stack (LTS releases have two kernel stack options; we don't even know if you're asking about server or desktop, so please be specific with questions).

ste

1/9/23, 7:23 PM

I tried the GA kernel and the desktop version. But the problem that I am describing seems to be pretty well known for Linux on Macs and quite independent from the distro used. Unfortunately none of the existing solutions worked for me so far.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Unable to boot Ubuntu 20.04 on iMac 12,2 (i7, Mid-2011) without kernel option `nomodeset`

TH: ไม่สามารถบู๊ต Ubuntu 20.04 บน iMac 12,2 (i7, Mid-2011) โดยไม่มีตัวเลือกเคอร์เนล 'nomodeset'

RO: Nu se poate porni Ubuntu 20.04 pe iMac 12,2 (i7, mijlocul 2011) fără opțiunea de kernel „nomodeset”

RU: Невозможно загрузить Ubuntu 20.04 на iMac 12,2 (i7, середина 2011 г.) без параметра ядра nomodeset

VI: Không thể khởi động Ubuntu 20.04 trên iMac 12,2 (i7, giữa năm 2011) mà không có tùy chọn kernel `nomodeset`

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