Installing Tiger on a G3 tray loading 333ghz iMac

I've done it, so I know it's possible.

Some requirements:

(1) Be sure you have installed the 1.2 firmware upgrade while iMac still has Mac OS 8.6 or 9.x on it.

http://docs.info.apple.com/article.html?artnum=60384

(2) Max out RAM to 512mb. Technically 256mb is the minimum requirement, but with the slow processor, small hard drive, and low-end video hardware, you need as much RAM as possible to compensate.

(3) A FireWire external case to use with the G4 iMac.

(4) If you plan to upgrade the stock 6GB drive, understanding of the 8GB startup partition limitation for the tray-loader iMacs (and some other models). Please ask a follow-up question if you need more info about this point.

The procedure - Remove the hard drive from the tray-loader iMac. Mount it in the external FireWire case. It is already set for Master, so you should not have to change any jumper settings.

Connect the external FireWire case to the iMac G4. Start up the iMac G4 using the Tiger DVD. At the Installer's screen, you may want to go up to the menu bar to Utilities and select to run Disk Utility. This is optional, but since the iMac's drive is old, you may want to erase it using the +Zero Out Data+ option (it's available using the Options button on the Erase tab). This type of erase writes zeros to all sectors, so it serves as a good +stress test+ for the drive to make sure it is working acceptably. Or you can do a normal erase.

After that completes, you have a freshly formatted drive. Quit Disk Utility to return to Installer. Select the tray-loader iMac's drive in the FireWire case as the target for the installation. Because the drive is already small, you should click on the Customize button and deselect all component you do not need. For example, not installing languages and printer drivers you do not need can save more than a GB of disk space. Not installing apps you do not need will save even more space.

Proceed with the installation. After it completes and the iMac restarts from the external drive, you can go through the initial setup as if it was the tray-loader iMac, and make sure the installation works. You can install all the updates now or wait. It may be a good idea to wait.

Finally, remove the hard drive from the external FireWire case and mount it back into the iMac. Try to start it up. It should work. There is nothing that prevents it from working. It's only the lack of DVD drive, and (if you have the CDROM set) the Installer that checks for supported Mac model, that prevents Tiger from being installed directly on the tray-loader iMac.

My difficulty is that I do not have a firewire external case to use with the G3.

It's probably a typo (above), but just to be clear, the FireWire case would be for connecting to the G4 iMac (since your G3 iMac does not have FireWire). And you run the Tiger installation using the G4 iMac, to install Tiger onto the temporarily relocated G3 iMac's hard drive.

I'm assuming there is no other approach to this challenge that will work?

Well, you can take apart your G4 iMac and temporarily replace it's internal drive with the G3 iMac's internal drive. Then start up the G4 from the Tiger DVD and run the installation as previously described. Then, take apart the G4 again to swap out the drives. But that would be a lot more work.

FireWire external drives are good to have for doing backups. I have one of these

[Macally external case|http://www.amazon.com/Macally-PHR-100AC-FireWire-3-5-Inch-Enclosure/dp/B00 00B3ALF/ref=pd bbs_sr4?ie=UTF8&s=electronics&qid=1225213768&sr=8-4]

which I bought empty and use with a drive purchased separately. It also has USB 2.0, so I can use it even if the computer does not have FireWire. There are cheaper external drive cases available, if you search online or use dealmac.com to find good deals.

If you happen to have a USB external drive handy, you can try it and see if the Tiger Installer will let you target it for the installation. However, since your Mac probably cannot boot from USB, you will been to complete the Tiger installation and immediately put the drive back into the G3 iMac before attempting a startup on the G4 iMac. But if the Tiger Installer does the installation to a USB external drive, I see no reason why that would not work.

No, that's not what I mean at all.

You need to put the actual hard drive that came out of the iMac G3 (and that you intend to use in that iMac G3 going forward) into an external drive case. Attach that external drive to the iMac G4. Let the iMac G4 run the installation, targeting that external drive for the installation. Run the installation and after it is completed, remove the actual hard drive from the external drive case and put it back into the iMac G3. Then start up the iMac G3 from the hard drive you just installed.

There is no way to use an iPod in this situation (that I can see), because there is no way to boot your iMac G3 from an iPod. There is no way for your iMac G3 to boot from ANY external drive. That's why you need to physically remove its internal drive and use another Mac to run the installation, because the installation disk is an unreadable (in the iMac G3) DVD.