16 January 2020
Most of the Apple G4 models dropped support for natively booting Mac OS 9 and only support Mac OS X. Through a lot of hard work the folks at MacOS9Lives.com have been able to get Mac OS 9 booting on most of these systems. Below is a compiled list of tutorials from my own experiences, and the others from MacOS9Lives.
There are a number of disc images available for multiple models at MacOS9Lives.com. I recommend burning these CDs with an application such as Toast Titanium.
Most of these machines have newer hardware that was never available for Mac OS 9, therefore there are missing drivers and system components - not all devices will work. The most common issues are with unsupported sound cards, video cards, Bluetooth, and Airport cards. The most success has been achieved with machines that have an ATI Graphics card/chip-set. Graphics acceleration is unavailable unless you have a graphics chip-set that is officially supported under Mac OS 9.
Before you install Mac OS 9 on your machine, your Hard Drive must have the Mac OS9 disk drivers installed. You can do this with either of the following methods:
This is achieved by performing some modifications in Open Firmware, and tricking your machine into thinking it has a different CPU version (This does not effect performance in OSX).
nvedit, and then press Enter.
dev /cpus/PowerPC,G4@0then press Enter
80010201 encode-int " cpu-version" property
device-endto close the CPU device.
Note: If there is text present after you open the NVRAM editor, these are settings that are already stored. You can either clear this by holding the delete key, or press the down arrow key for a new line, then you can start typing. When you open the editor you can think of it like you're viewing a document, but you're only seeing one line at a time. You can scroll through lines with the arrow keys. Once you're on a blank line you can enter any settings you'd like to add.
Performing the above only allows you to boot into Mac OS 9 temporarily. These commands need to be stored in the NVRAM so they persist between boots. Running the commands below will store this information in the NVRAM and restart the machine.
nvstore setenv use-nvramrc? true reset-all
Your machine will restart and you should now be able to boot from the Mac OS 9 For Unsupported G4’s CD from MacOS9Lives.com.
Any data stored in the NVRAM will be erased if the machine loses power (e.g. the main power cable is disconnected from a wall outlet/power adapter, or has a flat battery. Since this is a lot to type each time you lose power, a better way of performing the above is to write everything into a script, and tell Open Firmware to run it at boot. Now if you lose power you only need to remember one line to enter into Open Firmware.
Open Firmware Scripts can be created with the application ‘SimpleText’, or any other text editor that will allow you to save .txt files without any rich text content. Open SimpleText and add the following to your new document.
\ comment cr dev /cpus/PowerPC,G4@0 80010201 encode-int " cpu-version" property device-end boot hd:,\\:tbxi
The beginning of the script must contain an Open Firmware
\ comment, followed by a carriage return
The last line sets the boot device to the default HD so the machine continues to boot after running the script.
Save the file to the root/base directory of your hard drive and call it ‘bootscript’.
Some machines have incompatible sound cards and will crash or refuse to boot OS9 after the above steps have been taken. If this happens try adding the following to the NVRAM, or your script.
dev /pci@F2000000/mac-io/i2s/i2s-a " screamer" encode-string " compatible" property device-end
An example of this would look like the below:
\ comment cr dev /cpus/PowerPC,G4@0 80010201 encode-int " cpu-version" property device-end dev /pci@F2000000/mac-io/i2s/i2s-a " screamer" encode-string " compatible" property device-end boot hd:,\\:tbxi
Mac OS 9 does not have good thermal management for unsupported systems. If you're worried about elevated hardware temperatures under Mac OS 9, see the article Controlling System Fans with Open Firmware. You can combine both scripts to make things easier.
After booting successfully into Mac OS 9 you will need to install the system onto your hard drive. It’s a good idea to erase your HD with ‘Drive Setup’ if you don’t have anything important on it already.
If you install from one of the Mac OS 9 Lives CD images start the restore process and follow the instructions. Once the restore process has completed DO NOT restart your machine.
From the desktop, open HD > System Folder > Extensions and find the ‘Multi Processing’. Remove this folder by moving it to your desktop or to the trash. The extension(s) within this folder causes some incompatibilities with the unsupported systems and result in freezing during the boot process.
If you install from any other CD/image the same steps are recommended.
Once the system is installed and you have removed the ‘Multi Processing’ folder, restart the computer.
When you've booted into the newly installed system you may be stuck with a small screen resolution.
If your machine has an ATI Graphics chip-set it is highly recommended that you add this driver modified by darthnVader (alternative link) from Mac OS 9 Lives. This adds better compatibility with more resolutions and color depths. Expand the file with Stuffit Expander and move the extension to your ‘Extensions’ folder, which is located in the System Folder, then restart the computer.
If you've still got a small screen resolution, or limited colour set open the ‘Monitors’ control panel and adjust the monitor arrangement. First drag the menu-bar from the smaller screen to the bigger screen. This sets the default desktop. Next, change the screen arrangement by moving #2 to the left before #1.