The iBook G4 12" is one of my favorite Apple laptops, I love the way it looks and feels and it supports a wide range of operating systems. Officially it supports Mac OS X 10.3-10.5, unofficially however you can run Mac OS 9, as well as Mac OS X 10.2. Since Mac OS 9 supported some older G4 CPUs, you could run it on later G4 CPUs by spoofing an older one in NVRAM. Typically, I've seen this done using custom media, however I decided to have a go using official media.
Some caviats to running Mac OS 9 on the iBook G4 are:
Here is a bash script to set the NVRAM variables from Mac OS X, enabling you to boot Mac OS 9 (credit: Doggoli on Mac OS 9 Lives forum):
#!/bin/sh
echo "Enabling OS 9 booting..."
echo "You may have to enter your password"
# Use nvram command to setup nvramrc with script to make open firmware changes
sudo nvram nvramrc='" /" select-dev
" PowerBook4,3" encode-string " model" property
" PowerBook4,3" encode-string " MacRISC" encode-string encode+ " MacRISC2" encode-string encode+ " MacRISC3" encode-string encode+ " Power Macintosh" encode-string encode+ " compatible" property
00000000 " graphic-options" get-my-property 2drop !
unselect
" /cpus/PowerPC,G4@0" find-package if drop " /cpus/PowerPC,G4@0" find-device 80010201 encode-int " cpu-version" property then
device-end \ PLX-OS9-PATCH
'
# Enable use of nvramrc on boot. Change to "false" if you want to disable again. Or just clear/reset nvram.
sudo nvram "use-nvramrc?"=true
echo done.
If your iBook G4 loses power, the NVRAM gets reset and your variables get cleared. I recommend keeping Mac OS X installed to be able to run this script in the event your battery dies or you don't have one.
To start, the Mac OS 9.2.2 Universal CD-ROM is required, which has a sha256 sum of ba65d1ec2d6a3892233fabb555ca4ede7ff02156e5c671117d5a5d5ed440189d.
iso to a R/W .dmg using hdiutil.$ hdiutil convert -format UDRW -o macos-922-uni-rw macos-922-uni.iso
Mount the newly created .dmg.
In Finder navigate to the mounted dmg and go to System Folder/Extensions, then drag the Multiprocessing folder to the root of the dmg. For some reason Apple CPU Plugins causes Mac OS 9 to hang on the iBook G4.
Unmount the .dmg.
Convert the .dmg back to a UDTO - DVD/CD master image using hdiutil.
$ hdiutil convert -format UDTO -o macos-922-uni-multiprocessing-disabled macos-922-uni-rw.dmg
Burn the resulting .cdr file to a CD.
On the iBook G4 run the NVRAM script from Mac OS X.
Boot the CD on the iBook G4, make sure the Mac OS 9 drivers are installed on the hard drive. If they aren't you can either use target disk mode from another Mac to format the drive with the Mac OS 9 drivers over firewire, or you can use the Drive Setup utility from the OS 9 CD. However you should make sure to reinstall Mac OS X and keep them dualbooted so you can run the NVRAM script.
Install Mac OS 9 on the partition you want to install on, I recommend keeping Mac OS X and Mac OS 9 on separate partitions. However, they can reside on the same partition.
Continue and on the partition of the newly installed Mac OS 9 go to System Folder/Extensions/Multiprocessing and drag it to the root or delete it.
Now Mac OS 9 should boot, anytime the NVRAM gets reset (for example the battery dies) you need to rerun the nvram script.
Now, you may have noticed that at this point, the display is limited to 256 colors. This iBook G4 has an ATI Mobility Radeon 9200, and Mac OS 9 has a driver for the Radeon 9200.
To install the ATI Radeon 9200 driver you need the Radeon 9200 driver CD-ROM for Mac OS 9 with a sha256 sum of 6fedef96fd9423c2ba16b02c912d25310ad8ecf67b52eb2f1540af7119e54a41.
Now Mac OS 9 should be running in full color!
Most things seem to work as they should, but keep in mind this is an unsupported machine and there will be issues with it. I have not tested any applications that make heavy use of the GPU.