Has need for GUID partition crept in even for Snow Leopard

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Level 1

18 points

Has need for GUID partition crept in even for Snow Leopard

I bought this MBP 5,2 with Mountain Lion installed, but damaged probably by inept erasure or possibly wonky internal HDD

I never wanted 10.8 as I have a lot of important Rosetta/32 bit stuff. I was briefed to totally erase HDD and re-install, which after some difficulty I did using a Snow Leopard disk, & it ran fine for a week or so, when HDD totally failed. I carried on using the MBP while waiting for a new HDD booting from a Super-duper back up external HDD (made on a 2008 15" MBP), an arrangement that also worked well with our other Unibody 15" MBP whereby my wife ran her Queendom from the internal HDD, while I ran mine from the external

I 'restored' the new HDD from this same back-up, but could no longer use either HDD as a start-up disk. So I used original Install disk to try to install 10.6 (which previously hadn't worked at all). This time it stalled with instruction for a GUID partition, which I made in Disk Utility from the DVD. I was then able to complete the clean install which it followed up with instructions to import my data. However it would no longer allow use of the external HDD as a start-up disk.

So the final stage was to do a new Super-duper back up of the external HDD disk. All a little hairy with my last 15 years work at risk.

Can someone explain why the need for the GUID partition has come in (and when)? Is it just so one can install 10.8 later; when I first got the machine a partition seemed to be holding restore data? (but was insisting I sign up and pay up for my own lion)

MacBook Pro, Mac OS X (10.6.8), 17" June 2009

Posted on May 9, 2013 10:21 AM

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Answer 1

Niel

Level 10

726,719 points

May 9, 2013 10:28 AM in response to abderite

On an Intel Mac, Mac OS X will only install onto a drive partitioned as GUID; this is necessary for setting up Boot Camp and running firmware updates, but not to boot ths OS.

(82429)

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Answer 2

LowLuster

Level 6

12,105 points

May 9, 2013 10:36 AM in response to abderite

I pretty sure the above post is incorrect. The GUID partition table is needed because of the EFI firmware system on the intel macs. No EFI system can run with a MBR partition table drive. That goes for windows systems also. If the computer uses the UEFI then the hard drives in that system must be GUID (GPT).

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Answer 3

Niel

Level 10

726,719 points

May 9, 2013 10:41 AM in response to LowLuster

I was referring to GUID as opposed to the Apple Partition Map used on PowerPC Macs and not MBR.

(82431)

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Answer 4

LowLuster

Level 6

12,105 points

May 9, 2013 11:11 AM in response to Niel

Ok but your discription of why the GUID isn't correct. It is not only for firmware updates or for boot camp. It is because the intel macs use a EFI instead of a BIOS and all EFI system can only boot any os from a GPT (GUID) drive.

Now if a system has a legacy mode that mimics a BIOS then you can use a drive with a MBR PM. As for APM that went out 6 year ago when apple switched from ppc to intel cpus.

http://en.wikipedia.org/wiki/Apple_Partition_Map

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Answer 5

abderite Author

Level 1

18 points

May 9, 2013 12:38 PM in response to Niel

Niel wrote:

On an Intel Mac, Mac OS X will only install onto a drive partitioned as GUID; this is necessary for setting up Boot Camp and running firmware updates, but not to boot ths OS.

(82429)

So refusing to install may have a different reason from refusing as a start-up? And an external HD acceptable as a start-up with one internal HDD arrangement may not be acceptable with another?

Are HDDs marketed as 'for apple' just pre-partitioned accordingly, but otherwise no different?

If one erases the device as opposed to just a volume by mistake does that mean the partition has to be re-introduced?

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Answer 6

LowLuster

Level 6

12,105 points

May 9, 2013 12:44 PM in response to abderite

All hard drive are exactly the same. There are no windows only or mac os x only hard drives. It all about the formatting and partition table. Any drive manufactured today can work equally well in either a windows system or a mac os x system.

That also goes for ram and the cpus used in both systems. They are the same for each. That does not mean a cpu or ram made for a system 2-4 years old would work in a system built today or that a cpu or ram manufactured today would work in a system 2-4+ old. But for systems built on the same intel chipset the cpu and ram are interchangeable

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Answer 7

MartinR

Level 6

18,893 points

May 9, 2013 6:22 PM in response to abderite

On an Intel Mac, you can only install OS X on a GUID partitioned drive. The GUID requirement appeared in 2006 with the release of the first Intel Macs and continues to this day (on all Intel Macs).

You can create & use APM partitioned drives on Intel Macs, you just cannot install OS X on an APM partitioned drive in an Intel Mac. Here's a bit more infofrom Apple.

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