Installing Leopard on an unsupported Power Mac G4 “Sawtooth”

Last night, I got a 500-MHz Power Mac G4 (AGP graphics) to successfully install and boot into Mac OS X 10.5 Leopard. This took a little bit of doing, because Apple tried to thwart it by allowing only G4 Macs with a minimum clock speed of 867 MHz to install Leopard from the unmodified DVD.

Apple’s clock speed requirement was therefore the first hurdle I faced. My first stop was the how-to guide on MacOSXHints.com. The general idea is that you download and install xar (a program that compresses and decompresses installer packages, and comes with Leopard but not earlier versions of OS X), decompress one of the installer packages on the Leopard DVD, modify a file within the package that determines what Leopard’s clock speed requirement will be, recompress the installer package, and then make a copy of everything on the DVD (substituting our modified package) and boot off that copy in order to do the install.

Things immediately became difficult. I downloaded xar, but its configure program wouldn’t run. It was locating libxml2, one of xar’s dependencies, but it wasn’t finding xmlwriter.h. That file was apparently left out of the libxml2 distribution that comes preinstalled in Mac OS X 10.3.9.

So I downloaded a copy of libxml2, built and installed that, and then ran xar’s configure script again, only this time pointing to my newly installed libxml2 (since it wanted to keep finding the old one and aborting by default). Finally, xar built.

(I might mention here that although that doesn’t sound like it took a very long time, I’m not a Unix guru and don’t have a lot of experience with configure and make, and so there was a lot of trial and error involved in figuring out how to make this whole thing work. I’m also aware that I could have used the xar built into Leopard, which is already installed on my iMac Core 2 Duo, but I didn’t have the iMac available and I was determined to make it work the hard way.)

The next step worked without a hitch. Using xar, I decompressed the installer package. I edited the file to require only 400 MHz (my G4 is clocked at 500, but I figured I might as well give it a little room), and then I recompressed the installer package.

Next, I used Disk Utility to restore the Mac OS X Leopard DVD to an external USB drive. I figured that I could boot off that drive and install Leopard, no problem.

OK, two problems. The first problem was that the G4s had USB 1, and copying 7+ gigabytes from a DVD onto a hard drive over a USB 1 connection is very, very slow. The second problem was that apparently, this G4 won’t boot off USB drives. Oops. So that very, very long wait as the DVD was copied to the drive was for naught.

Luckily, nearby I had a G3 with two hard internal hard drives, one of them with plenty of space to hold that seven gigs worth of stuff. So I took it from the G3, put it into the G4, and waited as the DVD copied to that drive (faster than over USB, but still pretty slow).

With that all done, I picked the new drive in the Startup Disk preference panel, and rebooted the G4, expecting to see the Leopard installation screens. Instead, I saw a kernel panic; something about there not being a driver for PowerMac3,1 (Apple’s code for my particular G4).

I did some searching through Apple discussion groups, and discovered that the firmware could be an issue. The latest firmware for this G4 was the Power Mac G4 Firmware Update 4.2.8, and the G4’s current firmware was 2.x.x (don’t remember it exactly and didn’t write it down). Unfortunately, as you can see from the linked page, the firmware updater only runs on Mac OS 9, and that wasn’t installed on the G4.

Luckily, the G3 that had given up its second hard drive for the cause had OS 9 installed on the first drive. Unluckily, that hard drive seemed to be bolted inside the G3 case in a very secure fashion that I could not comprehend. There were no screws holding it in, so far as I could tell, but I couldn’t get the thing out of there. And the ATA cable in both the G3 and the G4 is a tiny little thing, so there was no way I was going to be able to attach the G3’s hard drive to the G4’s motherboard while the drive was still bolted inside the G3 case.

Unless… we open up computer #3. I had an old Dell nearby with a nice, long ATA cable, so I scrunched the G3 and G4 cases as close to each other as I could, and got the G3’s drive hooked up to the G4. Then I turned on the G3 (the hard drive’s power was still coming from the G3, because that cable wasn’t long enough), and once the hard drive had spun up, I turned on the G4.

First, it booted into the Mac OS X 10.2 installation that was also on that hard drive. Unhelpful. I selected the OS 9 installation in System Preferences and rebooted.

I didn’t think to hold down Shift and disable extensions. So it took 7 or 8 minutes for the G4 to start up OS 9, loading a whole ton of extensions. After all the extensions were loaded, the computer froze — apparently some sort of extension conflict. Goodness knows I haven’t played with pre-Mac OS X recently enough to have any hope of debugging extension conflicts. So I rebooted with Shift held down.

After getting through the “Welcome to Macintosh” screen, it popped a new box; apparently, the Multiple Users control panel was active and there was a password set. Unfortunately, I never used the OS 9 installation on the G3, and had no idea what the password could be. So back to the web (on computer #4, another Dell) to find out how to kill Multiple Users. Turns out that I could reboot in OS X, go into System Folder/Preferences, and delete Multi-User Prefs. OK. Done. Reboot back into OS 9 with extensions off, and I finally make it to the Finder.

So I try to fire up Internet Explorer 5.1, but apparently it needs an extension to even launch. So I fire up Netscape Communicator instead, and then discover that with extensions turned off, there is no internet connectivity. So I can’t download the firmware updater. I’d download it on the Dell and then move it over to the G4, but the G4 has no floppy drive. And I don’t really feel like burning a CD to move a 1.2 MB file.

So I reboot in OS X, download the firmware updater, and then back into OS 9. Run the updater, reboot holding down the Programmer Button, and the firmware updates. Woohoo - back in Jaguar, it’s showing that the firmware is now 4.2.8.

I disconnect the G3-G4 mess, put the Leopard-installer hard drive back into the G4, and finally! The installer starts up, Leopard installs, and all is right with the world.

It seems to be running great. Most actions seem more responsive than under Panther on the same system, but other things are obviously slowed down by the fact that the graphics card is doing almost none of the graphics work. (See the System Profiler image above; Core Image is “Software” instead of “Hardware Accelerated,” and Quartz Extreme is “Not Supported.”)