Mac OS 9 booting on: iMac G4 Flat

Mactron...

Can you ask iMac600 to post the Modified ROM taken from the OS9General.dmg ?

I think he did great work there, but dome newbies may be a little scared doing file Hex Edits...why re-invent the wheel if he can provide the modified ROM file.

We can repackage and make a "Beta Test OS 9 General" for testing on unsupported models (that are close in hardware spec. to approved models)

Here are my, relevant, specs:
Machine Model: PowerMac6.1
CPU Type: PowerPC G4 3.3
CPU Speed: 1GHz
Memory: 768MB
Bus Speed: 133MHz
Boot Rom Version: 4.5.9f1
Graphics: Geforce4 MX

I've only seen this OS9General mentioned alongside the MDD systems.

Would this OS9General work on a _supported_ iLamp system without a modified ROM?

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?

I have tried with the famous 9.8.1 Mac ROM from the diagnostic CD you mentioned but no luck again... however it comes at handy for future modifications because it already include in the initial part two extra Mac models that are:

PowerMac4,2 (iMac G4/800 MHz - 7450 CPU)
PowerBook4,3 (iBook  G3/900 MHz - 750fx CPU)

There's a thing that I suspect: the Diagnostic CD for G4 MacMini does not more contain a regular (modified) OS9 partition but another type of boot sequence, very similar to the one for the G5 machines and this lead me to look to what kind of processor is inside the OS9 PowerMacs...
Well, putting together the informations from the 68KMLA thread and the MacTracker database I discovered that...

NONE OF THE G4 POWERMACS WITH A 7447A/B CPU CAN BOOT OS9 NATIVELY!

So, what permit to the iBook 800 user in the other thread to boot os9? Simple: althought Apple disabled for this model (that has an ID equal to PowerBook 6,3) the OS9 support they build this machine with a 7455 inside and this is enough for the modified MacROM to load.

So, in the end, to have a universal MacROM file running on every G4 (and maybe G5) the real challenge is disable in the code the CPU check because THIS is the real issue in booting OS9, the text string in the beginning of MacROM it is only the first barricade, once removed all the G4 Macs with a 7455 CPU should be able to run OS9, but the 7447A/B Mac based needs to wait until someone really smart in PPC assembly can patch the ROM to disable this check.

At this point the only lucky users that benefit from the Mac ROM modding could be the iMacs users... this Mac family never adopted a 7447 CPU so the chances to have success in booting OS9 are higher than later PowerBooks, for example.

No problem :-) I have just done the modification using the 10.2.1 as base and 9.8.1 as reference for the right syntax during editing, I have a MacMini (7447) so this ROM does not work for me but I hope you will have better luck ;-)

Here is the link for the download

http://www.mediafire.com/download/a6ajgzsk346dzwa/MacOSROM_1021mod.zip

Please report your results here! Have fun! ;-)

!

Well, it shows up in the boot menu now! (My USB drive prepped with OS 9.2.2 install).
Naturally it won't boot though. I doubt OS9 can even be booted from USB? I tried that on my G4 Cube without any luck.

I guess I have to try to make a bootable CD. Good thing I've got media to spare. Just hope it's compatible.

First problem was that it didn't see the drive. I had to use the Drive Setup and create 2 partitions (just to be safe, not sure how well OS 9 and OS X will play together. OS X is nice to have for network transfers after all)

Then it tells me that "This program cannot run on your computer" when I try to launch the installer =S

I guess I either have to install using Target Disk Mode or try to make a new boot cd based upon the OS9General ?

I Installed the OS9General release on top of the plain classic stuff and it worked like a charm. Now I got a standard system up and running!

However I still only get 256 colors and sound doesn't seem to work. I'm guessing it's a fairly easy fix but I've got no experience whatsoever with OS 9 "drivers". Any takers? =)

Thanks SO much for the ROM file, this really got stuff rolling.