Talk:Apple Partition Map

Partitioning
I know that it is either possible for PowerPC Macs to boot GUID drives or for Intel macs to boot APT drives... I have specifically made external installations of Leopard that are bootable on both Intel and PPC platforms, so I know that one of these restrictions is false. AriX (talk) 14:45, 20 March 2012 (UTC)

I'd change "Mac OSX" to "Mac OS X". This looks strange. Is "both the" really correct? Not to maintain compatibility with earlier models, but to maintain compatibility with PowerPC-based models. Maybe this is more true: … on both architectures (PowerPC and Intel) in order to maintain compatibility with PowerPC-based systems. Although models of Mac computers that were sold with Tiger or Leopard are capable of a "booting" functionality, the ability to boot Mac OS X from APM disks on Intel-based Mac computers was not supported.
 * Yes, Intel-Macs can boot from APM partitions, but no PowerPC-based Mac can boot from a GUID partition.
 * While Intel-based Macintosh computers can boot from GPT and APM, Apple only supports booting Mac OS X on these machines from GPT. Apple's GUI tools, like the Installer, will prevent you installing Mac OS X for an Intel-based Mac on non-GPT disks.
 * It remains unclear if Apple actually left the possibility of booting from APM partitions in their current models – in this respect, the information provided by Apple seems quite outdated. (And Apple is known to remove outdated features–at least what they consider outdated for them–in future versions of their products…)
 * ‣Andreas• ⚖ 18:57, 20 March 2012 (UTC)
 * I worked solely on grammar, so forgive me if anything technical is now a problem Soulparadox 00:06, 27 March 2012 (UTC) — Preceding unsigned comment added by Soulparadox (talk • contribs)
 * I don't know about the grammar, but it sounds a bit non-technical now. But I guess this is okay because I'm not really in the position to tell how it sounds anyway (my English isn't that good).
 * What I noticed:
 * the official term is "Mac OS X", which I wrote with a non-breaking space (&amp;nbsp;) between the "OS" and the "X" to avoid getting them seperated due to line-breaks.
 * However, the installation media for both the Mac OSX Tiger and Leopard use APM…
 * … on the respective architectures of the PowerPC and Intel systems in order to maintain compatibility with earlier models.
 * I'd also change the first sentence to:
 * Reading though all of it again, I'm still not satisfied.
 * These are the facts I'd like to have in the paragraph:
 * Intel-based Macs normally use GUID partitioning, and are designed to boot only from GUID disks. (See PowerPC-Intel-Transition.)
 * Apple doesn't officially support booting from APM disks on Intel-based Macs.
 * Installation media of Mac OS X Tiger and Leopard are APM media, for compatibility reasons (so it can also boot on a PowerPC-Mac, which really is a MUST, because PowerPC is also supported by these versions of Mac OS X).
 * Apple officially supported (on Tiger and Leopard) booting on external hard disks from APM on both architectures (PowerPC and Intel). (Note: this may not work on newer Intel Macs. To be honest, I'm very certain it will not work, because there is no necessity for it. If an Intel-Mac isn't supported by Leopard, there really is no reason to support APM-booting on that model at all.)
 * Booting from an internal APM disk on Intel-Macs that came with Tiger or Leopard works, but is not and was not and never will be supported officially by Apple. Moreover, the Installer for Mac OS X will refuse to install the OS in an APM disk if the machine it is running on is an Intel-Mac. The reverse is also true: on a PowerPC-Mac it will refuse to install on a GUID disk (because it will not be bootable, obviously).
 * Additional information (the topic is Intel-Macs, so this is just a sidenote): PowerPC-based Macs cannot boot from GUID.
 * On all versions of Mac OS X starting with 10.4.2 both APM and GUID partitions can be used for data (but not for booting) – this functionality is not dependant on the architecture used.
 * Maybe you can but these facts together in a more elegant way… that really sounds English.
 * Anyway: thanks very much!
 * ‣Andreas• ⚖ 15:54, 27 March 2012 (UTC)


 * I did a complete re-write. Please go over it once more. Thanks, ‣Andreas• ⚖ 18:57, 28 March 2012 (UTC)

Intel-Macs boot from both APM and GPT partitioned disks – is it true?

 * For starting an operating system, PowerPC-based systems can only boot from APM disks msg01335 whereas Intel-based systems only boot from both APM and GUID disks. TN2166 Intel-based systems only install to GUID disks. It is possible to clone between the formats.

Is it true?

Can modern 2012 models really boot from APM disks? Still?


 * 1) Intel-based Macs that came with Mac OS X 10.4 and 10.5 had to be able to boot from APM disks due to the install discs, which were based on APM to continue support for PowerPC. Remember that 10.5 was universal: it could run on both PowerPC and Intel (IA32) Macs.
 * 2) That said, Macs that were delivered with Mac OS X 10.6 and later have no necessity for this function any longer. The Mac OS X install disc(s) for 10.6 were Intel-only.

It remains unclear whether Mac models starting with the release of Mac OS X 10.6 (2009) continue to have this function in their Apple-specific EFI implementation.

Knowing Apple, my guess is that they removed it; at least as soon as they went 64-bit with their EFI implementation.

I reverted this change, but I'm open for discussion on the matter. It would be great if someone owning a post-2009 Mac (one that came with 10.6) could try to boot from an APM formatted drive (containing Mac OS X 10.6??? which would be the minimum OS for such a Mac…).

‣Andreas• ⚖ 00:08, 5 January 2013 (UTC)


 * Regarding this change by Wikievil666:
 * It may still be that Intel Macs are able to generally boot from APM, but there is no operating system that would support this. Modern versions of OS X doesn't like to be started from an APM drive. Older Mac OS X versions, such as Leopard, are no longer supported on modern Macs, so there is no easy way to test this.
 * If someone has the means, knowledge and time: I would be happy to hear that an operating system is able to start on a, say, 2014 Mac from an APM partitioned drive. And if someone is able to hack a little: maybe even OS X is able to start from an APM partitioned drive. But please test this first.
 * Most referenced documents are from the era of Mac OS X Leopard. This was the famous universal operating system, running on both PowerPC and Intel. But since Snow Leopard, only Intel is supported. Sadly, there are no references available that would suggest that Snow Leopard and any later Mac OS X/OS X was able to boot from APM on an Intel Mac. Most reports rather indicate trouble when someone tries to do that…
 * ‣Andreas• ⚖ 19:12, 25 October 2015 (UTC)


 * Finally I got hands on a 2011 model Mac mini (MacMini5,2) and tested this with Mac OS X Lion (10.7.5). It successfully booted from an APM drive. (It won't install to an APM drive, but cloning from a GPT partition works.) I changed this in the paragraph.
 * ‣Andreas• ⚖ 07:18, 3 February 2016 (UTC)
 * Follow-up: For completeness, I did a test with OS X El Capitan (10.11.3) on an internal APM partitioned drive and it booted as well. Again, I cannot say for sure if this will still work on a newer Mac, but on a Mid 2011 Mac Mini it does. ‣Andreas• ⚖ 15:39, 7 February 2016 (UTC)

Template for navigation bar
I made a navigation bar for partition tables in german: Navigationsleiste Partitionstabellen. It may be a good idea to copy this to the english wikipedia. I don’t want to do it because I don’t want to interfere. If you find it to be a good idea thou, please go ahead and adapt it to your needs. In case of improvement I will be more than happy to backport it to the german Wikipedia. Thanks, ‣Andreas• ⚖ 12:39, 10 March 2013 (UTC)

Other partition statuses
I just ran the Apple HD SC Setup tool under System 7.5 and it wrote a partition map consisting of three entries: first a `MacOS/Apple_HFS`, for the substantial drive contents; second an `Apple/Apple_partition_map` to describe the partition map itself; third a `Macintosh/Apple_Driver` partition with the driver.

The MacOS/Apple_HFS partition was generated with a status of 0xb7, i.e. valid, allocated, in use, readable, writeable ... and bit 7 set. The other two partitions had bit 7 clear. The table in this article doesn't currently define a meaning for bit 7, but it clearly means something. Does anyone know the missing detail? — 209.249.190.124 (talk) 15:21, 17 September 2019 (UTC)