Currently I am doing this experiment on a MacMini 1.25 Ghz following the 68KMLA thread but until now it didn't work, the OS9 partition is still not bootable.
I have formatted the internal HD connecting the machine via firewire to my MDD and here I have discovered that "target mode" works only between onboard FW port while PCI firewire cards are not supported and if used for this purpose they tend to stop the machine from boot.
Using Disk Utility under 10.4.11 on MDD I have partitioned the MacMini HD in three parts paying attention to install the OS9 drivers too.
Then I have copied the files from OS9General.dmg image of my MDD's restore disk to the first partition of MacMini (all done through firewire connection) and proceed to modify the ROM file in System Folder.
The hex editor I used is HexEdit, I prefer it against HexFiend, in this case the byte lenght of edited file is shown in hexadecimal value instead of decimal. I do not like the way the Hexfiend screenshot are shown on 68KMLA because the ASCII part is too much simplified, it does not show for example the differences beween x00 and x20 that are rendererd both as a blank space, while of course they aren't.
However I have carefully performed the edit suggested, everytime unmounting the target volume before to reboot the MacMini but so far I have not luck in booting OS9 on that machine.
I have done the modification using two different ROMs:
9.5.1 from MDD's OS9General.dmg
10.2.1 from Classic installation included in OSX 10.4 Install Disc Set
Both ROMs comes from original discs I have, I am sure they are 100% Apple genuine, unmodified before.
I am not a programmer but looking at the code I see that the first part is nothing different to what various Unix bootloader do for allow the Mac to load a non-Apple OS, simply adding MacRISC3 and MacRISC4 to the MacRISC Compatibility string. This make sense and is a step in the right direction.
Then the right machine check is extended to "macrisc3" and "macrisc4" duplicating the case handled by the "macrisc" string.
Finally the "abort" command is replaced by the "clear" one and some characters in a subsequent empty space have to been cleared to rebuild the correct byte lenght of the file.
All this seems correct but also too much easy in my opinion :-) I wonder if this is really the only check done from the ROM to allow the OS9 environment to load, I mean in a modified ROM that want to work universally on every Non-OS9 PPC machine.
Maybe the modifications above are enough to cheat an iBook (if the reported steps on 68KMLA guide are complete) but not for the MacMini and maybe other machines.
I agree that the ROM to use is the 10.2.1 because is the more "neutral" since it is provided for Classic environment that runs both on G4 and G5 (but this do not mean that OS9 will ever run natively on PPC970 machines, the hardware resources are too much different).
I have done some reasearch on Google but wihout much success, how I can determine if a PPC machine is a MacRISC, MacRISC2, MacRISC3 or MacRISC4 ? Is there a reference table for that?
