I'm 95% sure that the problem can be solved (or at least ameliorated) with the right kernel arguments. Kernel arguments are hints/instructions that get passed to Linux so that it can boot itself properly.
Since your Mac is a native to Classic I'm going to assume that you're running
BootX. If so, you've got
four chances of getting it wrong ;-)
You'll notice the little text-area at the bottom of the dialog box when BootX kicks in. That's where you put your kernel arguments. Tacking on
video=radeon should do the trick. If you get a blank screen, then you may have to tinker with the
no video driver and
force video settings check boxes in the advanced settings - press the
Options... button on the dialog and you'll see them.
If my assumption was wrong and you're booting from CD or via OpenFirmware, then you'll have to type
linux video=radeon after you've chosen to boot YDL.
Please note that
video=radeon on its own may not be enough to get you going - you may need additional arguments, such as
vmode,
cmode,
resolution, etc. My PowerMac 9600, for example, needs to be fed
video=imsttfb:vmode:14,cmode:24 and
no video driver in order to show signs of life. You may need to do the same; then again, you might get it right the first time. Either way, be ready to scour the 'net for more info.
Addendum: I
thought the question
sounded familiar...