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[MacTron]

Enabling Mac Os ROM to boot on MacRisc3 computers (Os X only G4's):

Open the Mac OS ROM from the OS 9 system folder in Hex Editor. Be aware that this is written based on the ROM taken from the OS9General.dmg (Mirrored Drive Doors) version. Other versions of the ROM may be different or have different values.

First thing - and this is important - is to write the byte count down somewhere. If this changes, you will have problems. Of course it will inevitably change since we are adding some data to the ROM, but I'll show you how to correct this further down.

In the very first line, you will see the "COMPATIBLE" tags. In the case of the Mac OS ROM included with the OS9General.dmg system, there is only one value - MacRISC. In order to make this ROM detectable as a valid bootable system to the iBook (which is a MacRISC3 system), we need to add those as compatible systems. For good measure, I added both MacRISC3 (DDR-based G4s?) and MacRISC4 (G5-based?).

Next, you need to scroll down to the tag. You're looking for a line that looks like:

2dup " macrisc" $= r> or >r

Immediately after the $gt;r, I added the following (and spaces are important):

2dup " macrisc3" $= r> or >r 2dup " macrisc4" $= r> or >r

The idea here is to add those same additional models MacRISC3 and MacRISC4 as we added between the COMPATIBLE tags above, only here they're included in the "2dup" strings.

With these changes, the modified ROM will fail with a Checksum Error. To avoid this, you need to change the abort after checksum error to clear. It's possible another 5-letter command will work here too, but I used clear simply because it works.

Finally, after making the above modifications, the byte count of the ROM will have changed. Scroll down to the closing tag. After this tag is a large number of spaces (represented in hex as zeroes) for unused space in the ROM. Now, remember in the first step that you wrote down the byte count? What I did was delete some of these until the byte count matched exactly what I initially started with. Don't delete large blocks as pictured, delete them one by one. I only highlighted it to show the empty space.

Save the ROM and close Hex Fiend. If you're working in Target Disk Mode like I am, make sure you eject the OS 9 drive properly! Failing to do so will likely damage or fail to write the changes to the ROM file you just edited. I did this at least 5 or 6 times before I remembered to eject properly every single time.

The Result?

After making the modifications to the Mac OS ROM above, I restarted the machine with the Option key held down to enter the Startup Manager. Unlike before, the OS 9 drive and system folder is detectable as a valid boot device.

source:
https://www.thinkclassic.org/viewtopic.php?id=46

[supernova777]

awesome post 
amzing result + excellent guide mactron!

[Jakl]

Excellent Mactron!!
Now to find a macosx only G4 or "G5"
All my mdd's have been converted via Open firmware. 

[MacTron]

Thank You all, but this is just an HTML Copy/Paste from www.thinkclassic.org LOL

[MacTron]

Here show us how to achieve the same but with a few Open Firmware commands:

http://luttztfz.wordpress.com/tag/open-firmware-hack/

Even though this text is about "Installing Mac OS X 10.4 “Tiger” without the use of XPostFacto on an iBook G3 Clamshell without FireWire"

The main section show us how to enable "MacRisc2" (on a "MacRisc3" computer):

Code: [Select]

” MacRISC” encode-string encode+
” MacRISC2″ encode-string encode+
” Power Macintosh” encode-string encode+
” compatible” property


[Knezzen]

So this works? Can you boot Xserve's and FW800 MDD's into Mac OS 9?

EDIT: I found the post. Cool as hell 

[MacTron]

Thanks, but those are just "preliminary studies" ...

The xServe will be one of the hardest (the G5 are impossible). I'm waiting to do the real test -you know- LOL ...

[Rick Rhodes]

this is very interesting…   I am new here on the site…  I am a musician - recording engineer with much experience of DAW use…  since System 3.2 on a MacPlus so many years ago…  so I have a lot of experience pf using OS9 based DAW systems…

I really want to get my G4FW800 to boot and run OS9 reliably to set up a DAW with some legacy serial MOTU hardware and OS9 software…  using a Keyspan 4 port serial card to connect serial the interfaces…

at the moment I have this system running on a G4 450 AGP, but I would like to benefit from the extra processor power of the dual 1.25 G4 FW800…   I am on the process of doing a fan conversion on the G4 FW800 to make it nice and quiet !!!! )))

there is so much to read here about the G4 FW800 running OS9 and it is sightly confusing reading about all the experiments… I really appreciate the hard work that many of you have been putting in to get a G4 FW800 to run OS9…  good work, everybody !!  you know who you are !!

so…   I would really appreciate a simple, complete and definitive "how to" set of instructions to follow…

so… do I only need to edit the MacOS ROM in the the system folder ?   I don't need to modify anything else ? 
I do, of course, understand that the drives need to be properly formatted for OS9 by an OS9 Mac…  no problem at all via TDM…

and if anyone has any problems with an OS9 based DAW I am sure that I can be helpful… )))

pleased to be here on this forum…  thanks !!

keep up the good work, guys…

[GaryN]

Hey there Rick! Welcome to the party!

The 9.2-on-FW800 procedure is a piece of cake. NO complicated anything.

Download this OS and files from HERE:  http://macos9lives.com/smforum/index.php/topic,2143.0.html

Follow the instructions. They are, as you said "simple, complete and definitive". You'll be up and running in no time.

Also, consider loading 10.5 on another drive. My MDD is set up that way because I find it very useful to be able to occasionally access things not available to OS9.
You get easy internet access, the ability to use audio editors not available in OS9 and generally a way to interface with the rest of the world without major machinations.

The FW800 "experiments" are pretty much finished. The machine just works. FW800 ports operate as FW400. (adapter cables are handy). Airport, not so much - hardwire it. All else is normal.

Have fun!

[Rick Rhodes]

Thank you, GaryN !!!  sorry for the delay in replying…  I haven't been online for a while…  I really appreciate your assistance !   I am looking forward to a nice and fast OS9 on my G4 FW800 !!  as you suggest, I will probably keep an OSX (Leopard) drive to allow easy access to my network…   the limitation of FW400 is not a problem to me…  I have FW adaptor cables…  one of my old MOTU audio interfaces is an early 828 FW which simply refuses to work at all with FW800 or OSX… and I really don't need Airport either…

I will be very happy just to have a functioning and more powerful OS9 audio MIDI system to utilise my legacy interfaces and software…  the OS9 system that I am currently running on an old G4 450 AGP does work, but the old G4 450 (single processor) is struggling under the load…    and it is very easy to synchronise the system to my OSX audio MIDI system, with sample accuracy…

this is a very interesting site…  I really like OS9…  and have a lot of very useful OS9 software…  I really recommend Conflict Catcher as a startup manager…  I have always found that any active networking software (ethernet or AppleTalk) really interferes with audio and MIDI, so it is best to disable any network software…

anyway… thank you very much !!  I appreciate the hard work that went into making OS9 possible on a G4 FW800 !!