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Boot PowerPC Macs via USB 2.0 drives
Authored by: Ebonweaver on May 16, '06 04:05:14PM

I can confirm that this works under a 1.8ghz iMac G5
It was actually pretty cool to boot a machine from a 2gb flash drive (I trimed a copy of 10.4.6 down to 700mb and cloned it)

It does NOT work under a dual 2ghz G5 tower, or 1.67ghz 15" Powerbook. They don't have the "ud" device in firmware and I couldn't force it to boot from a USB line using similar techniques. As the above author mentioned, nothing shows the drive on these units, it's just not being scanned for.

I suspect only the iBook and iMac line have the "ud" device available which makes this possible, so no Powerbook or G5 is USB bootable. As a side note, once you add the "ud" boot device any time the mac boots up there is a momentary lost folder icon before it fails over to the internal hard drive.

Interestingly, older macs that only have USB 1 ARE USB bootable with no real tricks involved. While you can't select the USB device in the Startup Disk preference pane, you can simply option boot and choose the drive. It's slow of course, but it works.

The very interesting tidbit here is that the "ud" device does not show up in firmware on these old macs that boot from USB. This implies to me that Apple had the function in the firmware on the old machines to look at USB for bootable devices, then removed it when they added USB 2. This of course makes no sense as that's when you would have wanted it as it became truly useable with the higher speeds. Why the iMac and iBook have a partial ability to look for but not use such a device is very odd.

At any rate, I feel like every Apple support person and techy out there needs to flood Apple with requests to patch their firmware to allow USB booting, because it seems it should be a simple firmware update to allow it based on the above information.



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Boot PowerPC Macs via USB 2.0 drives
Authored by: Woofb on Sep 05, '06 11:20:53PM
There may be reasons not to boot from flash often.

I'm a switcher, and I remember looking up how to boot from USB if the bios supports it, and e-mailing somebody to ask why their shareware program didn't support booting from a flash drive.

They said flash drives can't handle quite as many read/write cycles as a hard drive, so it's not recommended for them to go through the hammering a boot sequence gives the drive as it creates and deletes files all over the place. (I have no idea how this translates to the Mac, but it seems to be common-sense that large modern operating systems do A Lot Of Stuff before you see your login, so I'd expect many tiny files to be created and deleted in XP and Tiger).

This suggests that booting from a flash drive all the time (for security or portability reasons) would not be good, because after a matter of weeks or months it might give up the ghost.

It occurs to me that this might mean a flash drive is a really good choice for a minimal system 'rescue disk' in the way people used to keep a boot floppy somewhere. This is because a flash drive seems to be noticeably more robust than floppy, zip, cd-r or hard drive, as far as keeping it lying about and expecting it to work is concerned. I haven't actually tried this myself (I tend to clone the main disc to the firewire disc and hope it all works), but it's an idea.

(Sorry if everyone already knows all this, but it's probably worth pointing out in case anyone's just thinking about it and falls foul of this)

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