Exclusive Photos: USB booting on Intel Mac


Peter Lin sent in a the first ever photos of new booting options on the Intel Macs, specifically the Intel iMac. Here you see the zoomed in capture of USB booting in action. Notice that the Startup Disk screen interface on the Intel Mac has vastly changed from the older, clunkier look on our PowerPC Mac.

Here are two more interesting photos:
New Startup Disk selection screen on Intel iMac. Notice the nicer, larger icons.
New Target Disk mode screen where you’ll see the larger Firewire icon displayed on the Intel iMac.

In a technical article entitled “Booting an Intel iMac from an External Drive“, TidBit writer Jonathan Rentzsch explains how Intel Macs change the Mac boot process in fundamental (and incompatible) ways:

The Intel-based Macs are the first Macs to use Intel’s Extensible Firmware Interface (EFI). Originally intended to replace the PC’s aging and unloved Basic Input Output System (BIOS), EFI has found its way into the new Macs, taking over for Open Firmware in PowerPC-based Macs.

Tagging along with EFI is a new partition scheme: GUID Partition Table (GPT); GUID itself is an acronym, expanding to Globally Unique Identifier. GUIDs are locally generated, world-unique random numbers, which make them handy for uniquely identifying all kinds of things without a centralized organization or database. GUIDs are a great way to identify hard disk partitions, enabling the operating system to track volumes even if the device interface changes (as would happen if you ripped your old hard drive out of your Mac and tossed it into a FireWire enclosure).

GPT replaces Apple Partition Map (APM) as the boot partition scheme for Intel-based Macs. And therein lies the rub. Intel-based Macs can’t boot from older APM drives, and PowerPC-based Macs can’t boot from newer GPT drives.

While the new partition mapping scheme divides booting compatibility of both generations of Macs, the ability to boot off USB disks on the Intel Macs does allow for interesting possibilities, including having dedicated USB flash drives for different applications, such as disk repair. So far BootCD from CharlesSoft has been said to allow you to produce a 700MB Mac OS X boot disk for your smaller USB flash drive.

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