I was having the problems described above installing Edubuntu Edgy on some of my wife's school's older G3 iMacs (400-500MHz, 256MB RAM). Note that with 128MB of RAM, these machines were basically useless (256MB and they're usable).
I managed to work around the problem described above as follows:
- Boot the Edubuntu 6.10 Edgy LiveCD
- At the boot prompt, specify single user mode with the "single" kernel option
boot: live single
- Once the machine comes up to a shell, Change the following in /etc/X11/xorg.conf (patch attached)
After that, I was able to run the live distro, and successfully perform an installation. Note that at this point, you're running X as root, which is generally not preferred).
Following the installation, the xorg.conf changes were preserved, which was nice. However, the additional kernel boot parameter "single" was also preserved. So after the installation completed, the machine rebooted again into single-user mode where I had to remove the "single" kernel boot option and reinstall yaboot via ybin.
# sed -i "s/single//" /etc/yaboot.conf
# ybin --verbose
After that, my installation worked fine.
To the Ubuntu developers... The proper monitor ranges should be detectable from ddcprobe at boot time on these machines, so I'd think you ought to be able to populate the HorizSync and VertRefresh properly in the next Fiesty ISOs. As for the DefaultDepth... This might ultimately be a problem with X for not failing back to a lower, working color depth. But for the sake of Fiesty ISOs booting on G3 iMacs (plenty still hanging around our school systems at least), any chance you could detect them, and special case their DefaultDepth down to 15bit?