Prior to the latest series of Intel Macs released this year, Apple had been using Open Firmware and their own proprietary disk partitioning system called APM. The new Intel Macs can read, but not boot, from existing APM drives. PowerPC Macs running Mac OS X 10.4.2 or later can read, but not boot, from GPT formatted disks.

Tiger is currently not Universal, so a Mac OS X boot disk has to be Intel or PowerPC specific. Therefore, the ability to boot both Mac architectures from the same type of disk isn't very important.

With Leopard, Apple will release one version of Mac OS X that installs and runs on both PowerPC and Intel Macs. After delivering Leopard, Apple will likely release new firmware for Intel Macs that removes any limitations from booting from the APM drives created by PowerPC Macs. This will once again allow a single drive to boot any Mac computer. It’s also possible, but more unlikely, that Apple will allow PowerPC Macs to boot from GPT drives.

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Contributed by: Daniel Eran, RoughlyDrafted Magazine