Install Mac OS X Leopard on a G4 800mhz Quicksilver

If you have an old G4 sitting around that’s at the 800mhz mark, you probably should try installing Leopard, because most people agree it actually runs FASTER than Mac OS X 10.4 Tiger. Weird, huh? I guess they’ve optimized the code pretty well.
However, when you try to install the operating system, you are warned that Leopard cannot be installed on your G4. There are a few reasons for this:
1) Leopard requires 512MB of RAM – you have RAM, right?
2) Leopard requires over 867mhz processor

We can fix number 1 by simply getting more RAM. I find Craigslist to be of great use here. Number two is a bit more difficult as G4 processor upgrades are ridiculously expensive once you consider the cost of a Mac Mini, and also requires a bit of tech savvy under the hood as you’d be swapping CPUs.
Not to worry, though. Here’s a way to convince OpenFirmware that your CPU is 867mhz, and allow the installer to boot, install, and get you off and running:
Boot into Open Firmware, I have covered this extensively here:
Once in OpenFirmware, issue the following commands (for single CPU):
dev /cpus/PowerPC,G4@0
d# 867000000 encode-int " clock-frequency" property
boot cd:,\\:tbxi

For dual CPU:
dev /cpus/PowerPC,G4@0
d# 867000000 encode-int " clock-frequency" property
dev /cpus/PowerPC,G4@1
d# 867000000 encode-int " clock-frequency" property
boot cd:,\\:tbxi

Note that all we are doing is over-writing the CPU clock-frequency (speed) property for each CPU installed, at boot time.
Also, if you need to boot another device, try:
printenv boot-device
This will return a list of boot devices to use when booting the installer. I used this in order to boot a Firewire device that had had a disc image (DMG) restored to it, making things a bit easy and faster.

Good luck!

Where’s my Mac BIOS? (How to get into OpenFirmware Easily)

A lot of people these days appear to be under the impression that Macs have a BIOS, which is unfortunate because they actually have something much better – Macs have OpenFirmware. This is true for G4 Mac Minis, PowerBooks, iBooks, iMacs, eMacs, and Dual G5s… I could go on and on.
I got most of this info from experience and the Apple Developper Connection – if you’re not a member yet, sign up, it’s free.

You can get into OpenFirmware using this key sequence:

CMD-OPT-O-F

In detail, this means using two hands, holding “command”, “option” and “f” on the left and “o” with your right hand. Do this while booting your computer and you well hear two chimes. At the end of the chimes you will be greeted with an

On my G4 Mac Mini, for example, I can hold down the power button for roughly 10 seconds and I will hear the chimes – this should work for iMacs as well.

The OpenFirmware prompt that looks like this:

ok

0>

Congratulations, you’ve accessed your “BIOS” you switcher!

Now that we’ve passed this glorious milestone, we have some work to do. After all you came here for a reason right? (and not just to click on the ads, wink-wink nudge-nudge)

Some useful commands that save me time and time again, and enable reparation of the G4 Mac Mini:

Boot your Apple computer using the default boot device:

0 > mac-boot

Boot your Mac using the inserted CDROM at the yaboot directory for linux CDs:

0 > boot cd:,\install\yaboot

To eject a CDROM from your Mac:

0 > eject cd

If you have any other OpenFirmware tips to share, feel free to comment!