Which partition scheme allows for the startup of PowerPC-based Macs?

The partition scheme that allows for the startup of PowerPC-based Macs is the Apple Partition Map (APM). APM was specifically designed to meet the requirements of older Macintosh systems, particularly those utilizing the PowerPC architecture. It provides a means for the operating system to recognize and manage the partitions on a storage device, facilitating compatibility with Classic Mac OS and the early versions of Mac OS X.

APM supports the unique structure and necessary metadata that PowerPC-based Macs require in order to properly boot from the disk. This makes it an ideal choice for these older systems, ensuring they can read and access their partitions effectively.

Other options like MBR and GUID serve different purposes or are oriented toward other hardware architectures. MBR is commonly used for Intel-based PCs and doesn’t support some features and larger drives that Macs need. GUID, while it is the standard for Intel-based Macs, is not applicable for PowerPC models, as those systems cannot recognize GUID partitions for booting. Lastly, ISO 9660 is primarily used for optical media, not for hard drives, and is not designed to support the booting process of Mac computers.