Cloning an already installed OS X to an APM partition on Intel systems will remain bootable even on 2011 Intel-based Macs. However, the installation of OS X on an Intel-based Mac demands a GPT partitioned disk or will refuse to continue, the same way installation on a PowerPC-based system will demand an APM partitioned destination volume. Intel-based models that came with Mac OS X Tiger (10.4) or Leopard (10.5) preinstalled had to be able to boot from both APM and GPT disks due to the installation media for these universal versions of Mac OS X, which are APM partitioned in order to remain compatible with PowerPC-based systems. the Compatibility Support Module provided by EFI).

Nevertheless, older Intel-based Macs are able to boot from APM, GPT (GUID Partition Table) and MBR ( Master Boot Record, using the BIOS-Emulation called EFI-CSM i.e. For starting an operating system, PowerPC-based systems can only boot from APM disks whereas Intel-based systems generally boot from GPT disks. Some hybrid disks contain both an ISO 9660 primary volume descriptor and an Apple Partition Map, thus allowing the disc to work on different types of computers, including Apple systems.įurther information: Mac transition to Intel processorsįor accessing volumes, both APM and GPT partitions can be used in a standard manner with Mac OS X Tiger (10.4) and higher. This means that every block on the disk (with the exception of the first block, Block 0) belongs to a partition. The Apple Partition Map maps out all space used (including the map) and unused (free space) on disk, unlike the minimal x86 master boot record that only accounts for used non-map partitions.

Because APM allows 32 bits worth of logical blocks, the historical size of an APM formatted disk using small blocks is limited to 2 TiB. The first block, Block 0, contains an Apple-specific data structure called 'Driver Descriptor Map' for the Macintosh Toolbox ROM to load driver updates and patches before loading from a MFS or HFS partition. ĭisks using the Apple Partition Map are divided into logical blocks, with 512 bytes usually belonging to each block. Computer disk partitioning standard for legacy Macintosh computersĪpple Partition Map ( APM) is a partition scheme used to define the low-level organization of data on disks formatted for use with 68k and PowerPC Macintosh computers.

Why partition disk mac