OS X Leopard On The Unimaginable G3

This project was created by christiann from MacRumors Forums in order to breathe new life into unsupported and relatively ancient hardware. Using these methods and tools, you will be able to install OS X 10.5 Leopard on your G3 Mac.

Pre-Install

A Macintosh that officially supports OS X 10.4 Tiger
A Macintosh that officially supports OS X 10.5 Leopard (for Method II)
512MB or more of RAM
A dual-layer DVD
Your selected OS X 10.5 Leopard image

Working Builds

9A241
9A241e
9A283
9a303

OS X 10.5 G3 Install Method I

Post-Install

Download your chosen beta build of OS X Leopard (up to 9A303). Extract it.
Mount the image and go to System/Installation/Packages. Inside ”Packages”, find OSInstall.mpkg. Right-click the file and open with TextEdit.
Open with TextEdit and delete OSmodelCheck.
Next, change hwbeSupportedMachines to the model identifier of the Mac you are installing it on.
Delete the BadMachines.
Change each "return false" to "return true" in the code below:

var minRam = 512;

function checkSupportedMachine(machineType){

// Fail on G3

if (1 != system.sysctl('hw.vectorunit') ) {

return false;

}

var badMachines = ['MacBook3,1','iMac','PowerBook1,1','PowerBook2,1', 'AAPL,Gossamer', 'AAPL,PowerMac G3', 'AAPL,PowerBook1998', 'AAPL,PowerBook1999'];

if(machineType){

var length = badMachines.length;

// Fail if any of the compatible values match the list of badMachines

for( var j = 0; j < length; j++ ){

if(machineType == badMachines[j]){

return false;

}

// require 867Mhz+

if (system.sysctl("hw.cpufrequency") < 866000000) {

return false;

}

return true;

}

Let’s edit the processor speed. In the code below, xxx represents the processor speed. Change "xxx" to "200", indicating 200MHz in the code below:

if (system.sysctl("hw.cpufrequency") < xxx000000) {return false;

Now, edit the RAM requirements. The minimum you should set this to is "512". (Make sure you have at least 512MB of RAM, but 760MB or above preferred). In the following code, change "512" to "400":

var minRam = 512;

Once you finished all of your edits, save the file with TextEdit.
Congrats! You have successfully edited the installer. Make sure that you saved your work. Now proceed to the install!
Burn the disk to a DL DVD and proceed as normal.

OS X 10.5 G3 Install Method II

Download your chosen beta build of OS X Leopard (up to 9A303).
Burn OS X to a DVD, and pop the disc into the officially supported G4 Mac.
Connect your G4 Mac and your G3 Mac via FireWire.
Reboot your G3 Mac holding the "T" key
Using your G4 mac, install OS X on the G3 Mac remotely.

Post-Install

Review the .pdf below for post-install assistance.

Leopard for unsupported Macs - installation and setup guide.pdf

The Classic Environment (9A241 Only)

It is possible to take the Classic Environment from a Tiger installation and run it.

Download the 9A241 build here and extract it.

Copy the System folder to your hard drive.

Copy the Classic Startup app from CoreServices from an install of Tiger to your install of 10.5 (9A241) in the same location. Copy the Classic prefPane to

Code:

/System/Library/PreferencePanes

Allow it to copy it to the destination, replacing files to get Classic to work.

in Terminal, run the following:

Code:

sudo chown root /System/Library/CoreServices/Classic Startup.app/Contents/Resources/TruBluEnvironment

Code:

sudo chmod u+s /System/Library/CoreServices/Classic Startup.app/Contents/Resources/TruBluEnvironment

Classic should now start. Currently speaking, it is slow to start.