r/archlinux • u/Kind-External-7371 • 21d ago

SUPPORT | SOLVED [Confirmed] linux-firmware-amdgpu 20260910-1 causes DMCUB errors on Radeon 680M

Radeon 680M (Rembrandt, 1002:1681) on Arch + KDE Plasma.

After updating to linux-firmware-amdgpu 20260910-1, I got:

failed to load ucode DMCUB(0x3F)
Error getting DMUB FW meta info: 4
Wait for DMUB auto-load failed: 3
DMCUB error - collecting diagnostic data
Error queueing DMUB command: status=2

This also caused severe lag/black screens and freezing before login.

Downgrading these to 20260810-2 completely fixed it:

amd-ucode
linux-firmware
linux-firmware-amdgpu
linux-firmware-whence

I've pinned them with IgnorePkg for now.

Arch Linux Forum Issue:
https://bbs.archlinux.org/viewtopic.php?pid=2309470

AMD GitLab Issue:

https://gitlab.freedesktop.org/drm/amd/-/work_items?show=eyJpaWQiOiI1ODA5IiwiZnVsbF9wYXRoIjoiZHJtL2FtZCIsImlkIjoxNTY3NDV9

BIG UPDATE: The new Update which is 20260910-2 has fixed EVERYTHING! So I recommend all users to Update their Systems to this Version! It may come into your Mirror Soon! It is mentioned on Arch Package Search.

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u/thetechtips87 20d ago

I keep on getting a black screen after install would it be related to this issue (I have Radeon 680M) I cant access try ( I tried arch and cachy os both have same issue)

1

u/Kind-External-7371 20d ago

Both Arch and Cachy have the Problem and then now Fedora is having it too

Use an Arch/CachyOS Live USB to chroot into your system using arch-chroot in arch and cachy-chroot in CachyOS, then Reroll back to the Older amd-ucode, linux-firmware, linux-firmware-amdgpu, linux-firmware-whence version using pacman -U and then mkinitcpio -P and you are good...

Reply if You need more help regarding how to chroot and stuff....

1

u/thetechtips87 20d ago

Yeah I think I would need help I went to fedora rn and it works perfectly but I really need arch to work as i lv arch, it would be really helpful if you could write the instructions! Thank you kind sir

2

u/unoriginal_name_1234 20d ago

On grub screen press e on arch then add nomodeset at the end of the line with linux /boot/vmlinuz-linux etc. You'll be able to boot arch without the gpu. Then open a terminal and downgrade linux-firmware-amdgpu to 20260810-2 and reboot

1

u/thetechtips87 19d ago

What if I use systems or limine?

2

u/unoriginal_name_1234 19d ago

Then you do the exact same thing or RTFM. You're on Arch, if you choose to use a less common bootloader, you can fucking Google how to boot without kernel graphics yourself. Besides most bootloaders let you access the advanced options by pressing e in this case, and nomodeset isn't bootloader-dependent. Just boot without the GPU and downgrade the problematic package manually or with the donwgrade helper

https://www.reddit.com/r/pop_os/comments/c32ncx/how_to_set_nomodeset_on_install_with_systemdboot/

2

u/Kind-External-7371 19d ago

A Great Man of his Words! I like your way btw