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epicMac's picture
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Joined: 2010 Nov 10
Best way to do this dual boot setup? (Mac Mini G4, 9.2.2 and 10.5.8)

So I have a Mac Mini G4 that I'm interested in getting a dual boot going for. I have the 9.2.2 install CD from macos9lives for the Mac Mini G4, with all the modified system files and such. The install CD seems to work best as a fresh install. This machine already has 10.5.8, I understand I'd probably have to wipe it though.

Assuming I have to start with a 9.2.2 fresh install, what's the best way to get 10.5.8 into a dual boot setup? I like to have both system folders on the same partition and just use startup disk to switch between them.

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Jatoba's picture
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Joined: 2018 Apr 16

Hello! What you want to do is possible, but there's one gotcha: while Mac OS 9.2.2's Startup Disk will allow you to pick either system, Mac OS X 10.5.8 Leopard's will not display the installed Mac OS 9.2.2 because it thinks the Mac mini G4 is not compatible and thus not eligible for booting (even though it is). There are some solutions to this, but the easiest one is to reboot from Leopard while holding down the Option key (also known as Alt) to switch to 9.

I'm not sure if you necessarily need to wipe clean your hard disk (more on that further below), although it'd be simpler to. The simplest procedure is, indeed, to wipe clean your drive with Drive Setup on OS 9, then install OS 9 on it, as per MacOS9Lives' instructions. Then, preferably on a separate partition, install Leopard.

It also works in the same partition, but jumping from Leopard to 9 via the "alt-boot" method described in the first paragraph, IIRC, will not be possible because the last-booted system will hide the other system (in this case, Leopard hides 9), forcing you to pick that OS 9 CD again just to boot from it and pick Startup Disk and select your OS 9 partition. I could be recalling that whole "hiding" thing wrong, though, but do be prepared for the possibility if you decide to go down this path. (Note: booting OS 9 from USB is also possible, but that's more technical to pull off.)

Now, if you don't want to wipe your disk clean installing OS 9, there is basically one thing you really need to do: You need to install what Mac OS X calls "OS 9 drivers". I forgot if doing this required wiping the disk clean or not. I think it does, but nonetheless, here goes the explanation on how to do this:

Again, since Leopard thinks the Mac mini G4 is not compatible with OS 9, when using Disk Utility, it won't show you the checkbox to trigger that, unless it's an external drive, like FireWire, USB etc. since, in those cases, the OS is "smart enough" to know those drives are more likely to be used on OS 9 computers than the internal drive. Of course, you can even exploit this fact by using a second Mac to use your Mac mini in Target Disk mode, which will allow the mini to be used as if it was an external hard disk, and be formatted with OS 9 drivers from Leopard itself.

Alternatively, there's a way to install OS 9 drivers regardless if Leopard thinks the mini is compatible with 9 or not, but this method requires using the Terminal app. If you are comfortable with using the command line interface (CLI), all you need to do is to pass an argument to diskutil which is "OS9Drivers" to have OS 9 drivers installed. This is what I personally have done, and it worked well for me. (I booted into Leopard via FireWire, wiped my internal disk clean, put OS 9 drivers on it, then OS 9 itself, and all final versions of OS X from Jaguar (10.2) to Leopard (10.5) in there, each system on a separate partition, then I used all the space I had for another partition to keep all my OS 9 and X programs on a Journaled HFS+ partition, which OS 9 uses without any problem. Later this year I'll just keep 9 and the programs partitions, then move the rest to a FW drive, since they see much less use, and the mini by far performs best with 9.)

I think this is enough information for now, but if you do run on any issues, please let us know. I'm an avid Mac mini G4 Mac OS 9.2.2 user here ever since it became available in early 2018, and I have seen a lot, so please feel free to ask any questions, and I'll address them the best I can.

Also, one last tip: it is rumored that you shouldn't use Spotlight or Time Machine on a drive with Mac OS 9, else you may come across something dubbed the "B-Tree" error (data loss). I never used Time Machine, and the few times I used Spotlight didn't cause me any issues yet, but do beware. Most people prefer to keep Mac OS 9 and Mac OS X very separate.

epicMac's picture
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Joined: 2010 Nov 10

Hmm, I hadn't realized Leopard would have issues like this on a Mac Mini. Is the process any easier with Tiger? I don't need Leopard specifically in this case, just some version of Mac OS X in case Mac OS 9 needs some assistance down the road. The detailed info on Leopard is greatly appreciated though.

Thing is I'm setting up a Mac Mini for a friend who wants Mac OS 9, but I'd like Mac OS X of some sort on there too. For myself I might try that 9.2.2 / 10.5.8 dual boot for my own Mac Mini, if I decide to move to that instead of my eMac.

Jatoba's picture
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Joined: 2018 Apr 16

Sadly, this restriction applies to all versions of Mac OS X that are compatible with the mini: 10.2 Jaguar, 10.3 Panther, 10.4 Tiger and 10.5 Leopard.

Theoretically, you should be able to spoof the machine ID on OpenFirmware to something that Mac OS X will recognize as OS-9-compatible.

I also personally speculate that there ought to be a .plist file for the Startup Disk prefPane to include the Mac mini's machine ID ("PowerMac10,1" & "PowerMac10,2") to a list of Mac-OS-9-compatible Macs that those programs are quite possibly consulting with. (Something like that would also probably enable installing OS 9 drivers via the GUI of Disk Utility to an internal drive.) I never came around to investigating/doing that, because 99.9% of the time I was using Mac OS 9 anyway. But I suspect it should be very doable!