Comment 7 for bug 569372

I have the same problem on my Radeon 5850.

When booting the live CD with default options, the graphical boot splash (Plymouth) works, although it runs at a low resolution (Presumably 640x480). Once the x server should take over the screen, the screen simply blanks, although the system continues to load (CD-seeking). The system continues to respond to key strokes, but using Ctrl+Alt+Fn does *not* produce a console and the system is thus unusable.

If I had to guess, I would say that the kernel is trying to use KMS (which is actually unsupported for Evergreen/R800, as madbiologist pointed out), which would explain the lack of a console (unless console hot keys are disabled like Ctrl+Alt+Backspace is on the live CD). I had the same issue, when I first installed my 5850 and I had to install fglrx to fix the issue on my Karmic + xorg edgers PPA + Lucid kernel. However, from vague memory, the Lucid Alpha 3 CD booted fine on the same system.

I was not offered to use fglrx during boot. I tried using "nomodeset", which had no effect.

Setting a "vga=" option caused Plymouth to boot at the selected resolution. However, it had no effect on the screen blanking.

I was unable to find a "safe graphics mode" or any menu option for booting to a command line with and without holding shift.

I also tried turning off ACPI via the boot option, which caused The graphical Plymouth splash to be replaced by what appeared to be a text version. However at the end of the boot sequence, instead of X starting up, a red "[Ok]" from the boot log appeared on top of the Text-Plymouth screen and the system appeared to hang.