Installing Tiger on unsupported Mac
Read the whole post and comments on jonSharp.net’s BLOG. It is WELL worth it, as some comments may prevent problem you could encounter.
Ok guys, I know what I said earlier about not getting Tiger to install, but I got to thinking about it and I had an idea. After digging around on the Tiger Install DVD, I found my answer. Here’s what I did to get the installer to install on my Lombard:
First, I created a CD/DVD master image from the Tiger Install DVD using Disk Utility.
Then, I mounted the image.
Then I found the OSInstall.dist file in /System/Installation/Packages/OSInstall.mpkg/Contents on the image. Near the top of the file is a line that specifies a list of “badMachinesâ€, or some such. In that list is “PowerBook1,1″, the model code for the PowerBook G3 Lombard. I simply modified that entry to read “PowerBook3,1″.
I then unmounted the image and burned it to DVD-R. My Lombard booted right up the installation DVD as it had before, but this time I received no error messages regarding unsupported hardware.
So, there you have it! It turned out to be much simpler than I had expected. Now, I must admit that I have not performed the installation of Tiger yet, so I cannot yet verify that the installation will complete successfully, but I plan to install a new HD in the machine and test it out at least before going back to Gentoo. I really don’t think Tiger will perform very well on this old machine, but it’s fun to try it out. 
Now, a note for Lombard users without a DVD drive: I would expect that you could perform the same operation on the CD version available as a special order from Apple.
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It’s even more easy to edit the bad machines list.
Just open the contents of the installation package OSInstall.mpkg by ctrl-clicking the package file in the Finder and choosing the option Show Package Contents in the popup menu list. A Finder window will show the package contents. Open the Contents folder and find in a glimpse the file OSInstall.dist. Open this file with TextEdit. Look for the line with the text ‘var badMachines …’, below the text ‘function checkSUpportedMachine…’, at the beginning of this file, which, by the way, is a scripting code file used by the installation application. Throw away any ‘bad’ machine out of the list within the square brackets. Take care to keep the remaining names, within two single quotes, in the list separated by a comma (no comma at the beginning and at the end of the list, please). And certainly do not throw away this variable declaration line. Keep it at least in a minimal form: var badMachines= []; (an empty list of bad machines), and no problem will ever arrive, except perhaps for the installation of that Tiger on a truly incompatible machine. Bad machines do exist. You can also try this, for the daredevil between you people: adapt the function that checks for a bad machine in such a way that it will always like any machine it finds. It’s easy to do so: just throw away the whole shebang in the function body of that function except fo the last line with the code ‘return true;’ (keep the semicolon at the end!). How to, would you say. Well, find in the OSInstall.dist file the line of text ‘function checkSupportedMachine(machineType){’, just above the line with the list of bad machines (’var badMachines = …’). And then throw away the lines of text starting with the text ‘var badMachines’ right through the line before the first line of text that has the code ‘return true; (‘just below the line ‘// if we can’t find it, …’). Keep the text ‘return true;’, a line of code necesary to have the installation software to like any machine. You can even keep the line of text ‘// if we can’t find it, …’. It’s just a line of comment in the code. But then, again, do not throw away the two slashes at the beginning of that line of text, or it’s no comment anymore. And, if you’re a kind of tabula rasa-type, you can do the same with the function that checks for a supported boot-ROM. But I suppose this will certainly give some après-ski problems…