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Summary:

I’ve been able to confirm that it is in fact possible to boot an Intel Mac and a PowerPC Mac from the same external hard drive, something that had been previously held to not be possible. The boot disks for the Intel and PowerPC versions of […]

I’ve been able to confirm that it is in fact possible to boot an Intel Mac and a PowerPC Mac from the same external hard drive, something that had been previously held to not be possible. The boot disks for the Intel and PowerPC versions of OS X do need to live on separate partitions, but the Intel partition can be formatted as APM, or Apple Partition Map, instead of the Intel-specific GPT, or GUID Partition Table. This is building on the great work of Jonathan Rentzch at http://rentzsch.com/tidbits/intelbasedMacBootIncompatibility.

What I did:

1. Partitioned a large Firewire/USB 2.0 external hard drive on my iMac with two partitions. Both were formatted as GPT, and were identically sized. One was named Intel Boot and the other PowerPC Boot.

2. Hooked the hard drive up to my test Intel iMac via USB and then booted the Mac off of the 10.4.4 install DVD that came with the iMac.

3. Installed 10.4.4 on the Intel Boot drive. (I left off the bundled software, so it was just 10.4.4.)

4. After the installation, I booted off of the external drive via USB 2 and made sure everything was working as expected. At that point, I also ran Software Update to make sure that I was up to date. Software Update found and updated my external drive with 10.4.5. Once the updates were finished, I booted back off the iMac’s internal hard drive.

5. Once booted from the internal hard drive, I used Disk Utility to make a cloneable image of the Intel Boot drive and saved that onto PowerPC Boot.

6. I disconnected the external drive from the Intel iMac, then connected it back to my G5 via Firewire.

7. I copied the Intel clone image from PowerPC Boot onto my G5. I then re-partitioned the drive again on the G5 and re-setup the Intel Boot and the PowerPC Boot partitions as APM-formatted partitions.

8. I then cloned the Intel clone image onto the Intel Boot partition, and cloned an existing 10.4.3 PowerPC image onto PowerPC Boot.

9. I booted my G5 off of PowerPC Boot and my Intel iMac off of Intel Boot. There appeared to be no problems.

This method obviously relies on building the image on an Intel Mac that has a GPT-formatted partition of sufficient size, but it does at least solve the problem of needing multiple external drives to support both Intel and PowerPC Macs. I used USB 2.0 in my testing mostly because I was testing the iMac’s ability to boot off of USB 2 as well. As far as I am aware, there’s no problem with booting an Intel Mac from FireWire.

Anybody had similar success? Let me know in the comments.

  1. sweet!

    more hardcore stuff like this please.

    cheers: dlf

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  2. Why don’t you actually explain what GPT is? And what utility allows me to format this way? I don’t see anything about the word GPT anywhere in disk utility!

    Explain yourself. Geeze, you would have been better off not writing the articile at all.

    HOW CAN I make a bootable (only for intel, i don’t care about my powerpc computers) USB external drive with Intel OS X on it (to hook to my macbook pro)

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  3. Court,

    Since I wouldn’t want to leave you underinformed in your quest to make a bootable drive for your MacBook, I’ll describe in greater detail how to partition your drive using GUID Partition Table, or GPT, in Apple’s Disk Utility.

    Starting with the version of Disk Utility that shipped with Mac OS X 10.4.3, a critical yet nondescript Options button was added to the Partition tab. Clicking it reveals a sheet that enables you to select the partition scheme prior to partitioning the selected drive.On the Power PC Macs, it allows two choices: Apple Partition Scheme (aka APM) and PC Partition Scheme (formats the drive for Windows, which the Mac can also read.) On the Intel Macs, it gives you a third choice, GUID Partition Scheme (aka GPT.) Partition your external drive as GPT and install OS X onto it from the DVD that came with your MacBook. Hit this link for a screenshot that shows both the Options button being referred to, and the various partition schemes available from Disk Utility on an Intel Mac.

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  4. Okay, I just followed your instructions on an external 400GB Drive (and a 1.83Ghz MacBook Pro with 100GB Internal Drive)

    I first set up a partion using the GPT, and installing 10.4.5 on a 50GB Apple Partition, then created a compressed image. (I also droped Carbon Copy Cloner and TechTool Pro on it)

    I then used disck utility to repartion it as follows:
    instead making 4 partitions (Using PC Partion Scheme),

    (A) 50GB FAT32 (I plugged it into my PC and Converted it to NTFS),
    (B) 50GB Apple Partition,
    (C) 100GB Apple Partion,
    (D) the remaining ~170GB Fat32

    I then Recovered the image to the 50GB Apple Partion.

    I was able to boot the the (B) 50GB Apple Partition (using PC Partition Scheme) and am now in the process of Cloning my internal hard drive to the 100GB external Drive partion (Apple Formated)

    All the drives are visable on the Mac (although the NTFS is read only). And I can boot to (B) drive. So it appears that the only limitation is that you have to install to a GPT, but you can boot from a PC Partion Scheme drive that has a recovered image on it.

    Thanks for the post, I was banging my head against this for a couple of hours.

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  5. Fantastic and informative thank you. So what about an Intel Mac’s internal drive? Is there any way to explicitly force GPT partitioning on it? Disk Utility is totally mum on the subject, as described in Jonathan Rentzch’s article. I don’t have a 2nd intel mac so target disk mode won’t help me here (the 2nd PPC mac shows the options button as described in your article, but GUID Partition Scheme doesn’t show up as an available config since a PPC Mac can’t understand it anyway).

    You can probably figure out what I was doing to get the internal drive in a non-GPT state ;-)

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  6. All fixed! you need to explicitly erase the partition. once done highlight the drive in disk utility and click on the info button. make sure it says “GUID_partition_scheme” on it.

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  7. “…On the Intel Macs, it gives you a third choice, GUID Partition Scheme (aka GPT.)”

    Uhm, is it named differently orso? On my MBP I can only see the following options:
    Mac OS Extended Journaled
    Mac OS Extended
    Mac OS Extended Case sensitive, journaled
    Mac OS Extended Case sensitive

    Unix
    Free Space

    So, which one should I use to format a partition to GUID?

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  8. http://www.macobserver.com/tip/2006/08/16.1.shtml

    Read this site to see where to find the missing Partition Scheme commands within Disc Utilities…they are there, you are just selecting the wrong item in the list of drives such that you are not seeing the commands you need! I was having the same issue as you and asked around and a fellow worker gave me the link above to save the day!

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  9. #2 Court Kizer says:

    Explain yourself. Geeze, you would have been better off not writing the articile at all.


    Whiney little bitch –

    Great Article

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  10. Hi,
    I may have jerked myself around but…
    If your partition or hard drive is partitioned for 4 partitions and they were originally done on a non intel based machine can disk utilities re format with the GUID scheme? I have to assume not but never hurts to ask.
    Guess I should have left half the drive “free” then I likely could have had 2 schemes on the drive. I want separate boot images so I can have an external drive boot whatever Mac I need – intel and no intel machines.

    Thanks folks

    Bill

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