Excited about Leopard’s super cool groovy new features, but your Mac doesn’t meet the stiff new system requirements? According to Apple, Mac OS X 10.5 Leopard cannot be directly installed on Macs with a G4 processor slower than 867 MHz. However, provided that you have access to a Leopard compatible Mac, there is a workaround. I discovered while trying to get Leopard working on my 800 MHz Titanium Powerbook, that while it can’t be installed directly, it will run from a drive with Leopard already installed.
So here is what needs to be done. First, get a Leopard compatible Mac. Take the older Mac start it up in target disk mode and connect it to the LCM (Leopard Compatible Mac) via a Firewire cable. Insert the Leopard installation disk in the LCM and start the installation process. When the installer asks where Leopard is to be installed, specify the Target Disk Mode connected Mac’s hard drive. Complete the installation process and once the LCM has happily booted from the new system shut it down, disconnect the older Mac, and power it down. Start the older Mac up and it should now be running Leopard.
Some caveats before doing this your own.
First: Running Leopard on Macs that do not meet the stated system requirements is not supported by Apple and they will not provide Leopard technical support for this configuration. Do this at your own risk.
Second: Do not use this technique from an INTEL-based Mac, only use qualified G4 or G5 processor Macs. The partitioning scheme for INTEL Macs is different and INTEL Macs can’t boot from drives formatted to boot PowerPC Macs and vice versa.
Third: Older Macs may not have enough processor horsepower, bus speed, or video RAM to effectively run Leopard (Forget about G3 Macs, there’s a reason they are excluded from the system requirements. Trying to boot a G3 Mac from a Leopard drive results in a kernel panic, I’ve tried). Leopard works just fine on my 800 MHz Powerbook, but older 400 MHz systems with a sub-200 MHz bus, and less than 32 MB of VRAM may have problems (unsure of your Mac’s specs, download Mactracker, a database tracking all Macs models ever made, www.mactracker.ca).
Fourth: Before you attempt this tip, be sure to back up all your critical data (maybe even clone the boot drive). Never perform major upgrades of any kind without backing up.
Trying to give an older Mac new Leopard super coolness, could work out great, or it could be time for a new Mac.