[Veltliner]

I understand that you have to format a partitioned, external disc in GUID if you want to use it as an emergency start-up disc.

The Apple Partition Map is for starting up PPC Macs.

I partition this external hard drive in GUID, can I still use it with a PPC Mac - just not as a start-up disc?

How rigid are those disc partitioning formatting standards, and how exclusive are they?

[reader50]

APM = required to boot a PPC Mac, whether internal or external drive. Will boot an Intel Mac from an external drive.
GUID = required to boot an Intel Mac from an internal drive. Can boot an Intel Mac from an external, but will not boot a PPC from internal or external.

Either partition map works fine for a data disk. It only affects booting. Apple ought to release some firmware updates for the recent PPC Macs so they can boot from GUID - but so far, they haven't done so.

[Veltliner]

Thank you, reader50.

Great to have this confirmation before actually doing it.

[hookem2oo7]

if i'm not mistaken... Only PPC Macs running Tiger (something like 10.4.6+) can read GUID formatted disks...

[Simon]

DiskUtility support for GUID on PPC Macs was introduced with 10.4.6.

[.Neo]

Originally Posted by reader50 

APM = required to boot a PPC Mac, whether internal or external drive. Will boot an Intel Mac from an external drive.

Are you sure about that? From what I understand Intel-based Macs only boot from GUID partitions, regardless if they're internal or external.

[CharlesS]

It boots fine, but it's hard to get the OS on there in the first place, because the Installer might refuse to do it. If that happens, you have to clone an OS on there from somewhere else, but you can make it boot, IIRC.

[Art Vandelay]

Yes, Intel Macs can boot from APM partitions. The Install DVD for Intel Macs is APM. Intel Macs have to be able to boot from APM disks if Apple wants to be able to provide a single Universal Install DVD for Leopard that boots both PowerPC and Intel Macs, as they intend to do.

[.Neo]

Originally Posted by Art Vandelay 

Yes, Intel Macs can boot from APM partitions. The Install DVD for Intel Macs is APM. Intel Macs have to be able to boot from APM disks if Apple wants to be able to provide a single Universal Install DVD for Leopard that boots both PowerPC and Intel Macs, as they intend to do.

Definitely good to know that. A lot of sites state there's no universal partition map for both Intel and PPC Macs.

[Art Vandelay]

I think a lot of people believe that because the OS X installer won't let you install onto a APM disk on an Intel Mac, as CharlesS said.

[reader50]

Can anyone confirm if an Intel Mac can boot from APM on an internal HD? Last I heard, shortly after the Intels came out, they would boot from APM on an external HD, but not from an internal HD.

[CharlesS]

I don't have an Intel Mac, so I can't try it to find out for sure, but I can't imagine there'd be that much of a difference between an internal vs. external hard disk.

[Art Vandelay]

I can try it tomorrow at work.

[angelmb]

so if you are trying to install Leopard into a 'non supported' 800 MHz G4 iMac from a MacBook via Target Disk Mode and the installer only lets you to format the iMac internal hard disk as GUID… what would be a workaround since it is obvious the iMac isn't going to start up from a GUID partition table… ??

[Person Man]

Originally Posted by angelmb 

so if you are trying to install Leopard into a 'non supported' 800 MHz G4 iMac from a MacBook via Target Disk Mode and the installer only lets you to format the iMac internal hard disk as GUID… what would be a workaround since it is obvious the iMac isn't going to start up from a GUID partition table… ??

You'll have to install somewhere else, and then clone that to the G4 iMac with Carbon Copy Cloner or something.

[angelmb]

Thanks, that was what I guessed I would ended doing… anyway let me ask: to do the same procedure albeit with a PowerBook (PowerPC) instead of a MacBook (intel) would bypass the GUID thing though and let the iMac to boot… with the iMac attached to the MacBook the installation gets done but of course then, the iMac is not able to boot from its very own hard disk which got the 'GUID treatment' before…

[Person Man]

Originally Posted by angelmb 

Thanks, that was what I guessed I would ended doing… anyway let me ask: to do the same procedure albeit with a PowerBook (PowerPC) instead of a MacBook (intel) would bypass the GUID thing though and let the iMac to boot… with the iMac attached to the MacBook the installation gets done but of course then, the iMac is not able to boot from its very own hard disk which got the 'GUID treatment' before…

From the PowerBook, just reformat the iMac as APM.

[angelmb]

Done the iMac is running 10.5 yet, and it is surprisingly good enough… damn*t I am tempted to install it to this old B&W I have around here