New Partitioning Options with Intel Macs
If you have attempted to partition an external drive to include an OS boot disk on a new Intel Mac, you may have noticed a few options. In Disk Utility, you have three options for partitioning.
GUID Partition Table - used to create a boot disk for an Intel-based Mac.
Apple Partition Map - used to create a boot disk for Power PC Macs, or non-startup disk for any Mac.
Master Boot Record - used to create a boot disk for DOS/Windows machines.
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Note: If you select the volume (i.e. “Macintosh HD”, etc) in Disk Utility, you will not get the “Partition” option. That is only available when you select the drive, as pictured below.

