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How can I disable the faulty AMD dGPU on boot on my MacBook Pro 8,2 and only use the Intel HD3000 iGPU?

jp flag

I know there are other threads about this but when I try to follow the instructions, I just end up with a black screen.

I have a 2011 15" MacBook Pro with the defective AMD GPU. I have Mac OS Monterrey working on it using the excellent Opencore Legacy Patcher but there are some glitches with OCLP so I have also installed Ubuntu 22.04. For some reason, the ALT boot wouldn't detect an Ubuntu USB so I ended up installing it from a DVD using legacy boot. As expected, when I boot Ubuntu like this, the screen fills with black and green rectangles and eventually the computer crashes.

I followed the instructions on https://www.variadic.xyz/2020/06/15/ubuntu-2011mbp/ to modify Grub but this just means that I get a black screen.

By removing the outb and i915 commands but leaving the radeon.modeset=0 I managed to get a readable but distorted screen with black and green vertical stripes.

Before I upgraded to Monterrey, I did have Ubuntu 20.04 working really well with the AMD GPU disabled and no screen artifacts so it should still be possible...

Any tips on how to disable the AMD dGPU on boot from Ubuntu 22.04 would be most welcome.

us flag
What is OCLP? Is it a program in MacOS? Can it affect the GPU when Ubuntu is running?
Simon Baldwin avatar
jp flag
OCLP is short for Opencore Legacy Patcher, it runs in Mac OS to enable the installation of newer, unsupported OSs. I think it modifies the NVRAM so could affect the way that Ubuntu works. It includes patches to disable the AMD GPU to improve compatibility with later versions of Mac OS.
David avatar
cn flag
To summarize you have a machine over 11 years old with defective hardware and you want to run Ubuntu on it?
Simon Baldwin avatar
jp flag
That's it! It has a perfectly good iGPU, an i7 and 16GB of RAM. Apart from getting the display working it runs Ubuntu pretty well.
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