Startup from external HDrives

[PlantDock]

Can Mac's be started up from external USB2 drives or is external startup limited to firewire only?

I have several machines, Imac ( all four flavors ) Mac Book and Pro.

I want to use Time Machine as the back to all of these devices but I hesitate because of this possible restriction.

Thanks in advance.

PlantDock

 

[DeltaMac]

A PPC Mac (such as a G4 or G5) will not boot from a USB drive.
Any Intel Mac can boot from a USB drive, so your answer about booting from USB, is yes, depending on which Mac you have.

Your other inquiry is about booting to a Time Machine backup, well, no, a Time Machine backup is not bootable, so the USB drive would be usable for Time Machine, even if it can't boot the Mac that created it. That's not how the Time Machine works - the backup file can't boot the Mac that created it.
If you need to use the Time Machine backup, you would boot to your Leopard install DVD, and choose the Time Machine backup for a restore.