Old Radeon card messing up OpenCL on newer AMD card

Hi. Is there a way to blacklist the radeon driver from a specific GPU? I want to setup a box that uses an OLD radeon card (6570 so Northern Islands card) to display a very basic desktop and use a newer AMD OpenCL enables card to crunch some openCL numbers in the background. However when the radeon driver gets loaded clinfo gives me this error:

amdgpu_device_initialize: DRM version is 2.50.0 but this driver is only compatible with 3.x.x.

If I blacklist the radeon driver, my OpenCL works, but I can not get a desktop on the old card. Any Ideas to get these to play nice?

You need to create a .conf file in /etc/X11/xorg.conf.d/. First check that a default file, created automatically to setup video (not keyboard nor mice, etc.), is not present. If it is, rename it, for example, with the extension .conf.bak.

Then get the BusID of both cards: lspci | grep VGA.

Then write a basic file, called, for example, 99-video.conf (99 will ensure it loads after, and overrides, any posterior file automatically created by the system). Example:

# Graphic card config file

# There are a bunch of options you can enter in the Monitor section, but it's not mandatory.
# The Monitor section is here so you can tie a specific card with it. You can create more than one section if you have more than one monitor section, but in case you may need to identify each monitor with more options.
Section "Monitor"
    Identifier "Monitor0"

Section "Device"
    Identifier "OldCard"
    Driver "radeon"
    BusID "PCI:0:1:0" # just an example, you need to check this
    Option "TearFree" "true" # you may need this or not
    # this will tie this card with the Monitor section Monitor0.
    #VGA is the name of the output being used. You need to check it with xrandr - this is just an example (it will probably be HDMI-0 or something like that.
    Option "Monitor-VGA" "Monitor0"

Section "Device"
    Identifier "NewCard"
    Driver "amdgpu"
    BusID "PCI:0:2:0" # again, check this carefully with lspci

This is the basis for the file. You should check this before you proceed. Take your time, and don’t forget to have a bootable USB at hand, because you may not be able to boot if you get it wrong (you can always enter another tty, login and rename the file to another extension, of course).